Prospectus Supplement No. 1

Filed Pursuant to Rule 424(b)(3)

Registration File No. 333-251390

Rush Street Interactive, Inc.

16,043,002 Shares of Class A Common Stock

PROSPECTUS SUPPLEMENT NO. 1

DATED MARCH 10, 2021

(To Prospectus Dated December 29, 2020)

This Prospectus Supplement No. 1, dated March 10, 2021 (“Supplement No. 1”), is being filed by Rush Street Interactive, Inc. (the “Company”) to update and supplement the information contained in the Company’s prospectus, dated December 29, 2020 (as amended and supplemented from time to time, the “Prospectus”), related to the resale from time to time by the selling stockholders named therein or their permitted transferees of up to 16,043,002 shares of Class A Common Stock, par value $0.0001 per share, of the Company, with the information contained in our Current Report on Form 8-K, filed with the Securities and Exchange Commission (“SEC”) on March 10, 2021 (the “Current Report”). Accordingly, we have attached the Current Report to this prospectus supplement.

This prospectus supplement updates and supplements the information in the Prospectus and is not complete without, and may not be delivered or utilized except in combination with, the Prospectus, including any amendments or supplements thereto. This prospectus supplement should be read in conjunction with the Prospectus and if there is any inconsistency between the information in the Prospectus and this prospectus supplement, you should rely on the information in this prospectus supplement.

Our Class A Common Stock and warrants are traded on The New York Stock Exchange under the symbols “RSI” and “RSI.WS,” respectively. On March 8, 2021, the closing price of our Class A Common Stock was $15.28 per share and the closing price of our warrants was $3.75.

Investing in our securities involves risks that are described in the “Risk Factors” section beginning on page 15 of the Prospectus.

Neither the SEC nor any state securities commission has approved or disapproved of the securities to be issued under this Prospectus or determined if the Prospectus or this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus supplement is March 10, 2021.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): March 10, 2021

RUSH STREET INTERACTIVE, INC.

(Exact name of registrant as specified in its charter)

900 N. Michigan Avenue, Suite 950

Chicago, Illinois 60611

(Address of principal executive offices, including zip code)

Registrant’s telephone number, including area code: (312) 915-2815

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company x

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

On March 10, 2021, Rush Street Interactive, Inc. (the “Company”) issued a press release announcing the Company’s financial results for the fourth quarter and year ended December 31, 2020.

A copy of the Company’s press release is attached hereto as Exhibit 99.1 and is hereby incorporated by reference in this Item 2.02. The information and exhibit contained in this Item 2.02 is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, except as shall be expressly set forth by specific reference in such filing.

(d) Exhibits

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Exhibit 99.1

RUSH STREET INTERACTIVE ANNOUNCES FOURTH QUARTER AND FULL YEAR 2020 RESULTS

- Fourth Quarter Revenue of $100.0 Million, up 260% Year-over-Year -

- Full Year 2020 Revenue of $278.5 Million, up 337% Year-over-Year -

- Full Year 2021 Revenue Guidance Raised 37% to between $420 and $460 Million -

CHICAGO - March 10, 2021 – Rush Street Interactive, Inc. (NYSE: RSI) (“RSI”), a leading online casino and sports betting company in the United States, today announced financial results for the fourth quarter and full year ended December 31, 2020.

Fourth Quarter 2020 Financial Highlights

Full Year 2020 Financial Highlights

¹ Includes $13.4 million and $41.5 million for the fourth quarter ended December 31, 2019 and 2020, respectively, and $13.4 million and $144.7 million for the year ended December 31, 2019 and 2020, respectively, of non-cash share-based compensation related to partnership interests in Rush Street interactive, LP that were issued before the Business Combination between Rush Street Interactive, LP and dMY Technology Group, Inc., which completed on December 29, 2020.

² This is a non-GAAP financial measure. Please see “Non-GAAP Financial Measures” for more information about this non-GAAP financial measure and “Reconciliations of GAAP to Non-GAAP Financial Measures” for a reconciliation of the most comparable measure calculated in accordance with GAAP to this non-GAAP financial measure.

Greg Carlin, Chief Executive Officer of RSI, said, “We are proud to be reporting our first financial results as a public company. Throughout 2020, RSI continued its rapid expansion in both new and existing markets achieving revenue growth of 337%. We were the second largest online casino operator in the US for the fourth quarter and full year 2020 according to Eilers & Krejcik.

We achieved these strong results with a modest 2020 marketing expense of $56.5 million. Our significant cash balance at year end plus the incremental cash from our ongoing warrant redemption will allow us to significantly increase 2021 marketing spend and leverage what we believe to be industry leading acquisition costs, payback rates, and average revenue per user. We are significantly increasing 2021 guidance and intend to aggressively pursue opportunities for further growth now that we are better capitalized than at any time in our operating history. We are confident these additional investments will support our goal of being the leader in online casino and driving significant profitability over the long term."

Increasing 2021 Revenue Guidance

RSI expects revenues for the full year ending December 31, 2021 to be between $420 and $460 million, up from our previous guidance of $320 million. At the midpoint of the range, revenue of $440 million represents 58% year-over-year expected revenue growth when compared to $278.5 million of revenues for 2020. This increase reflects our strong Q4 2020 results and anticipated growth in recently opened and existing markets resulting from increased marketing spend funded with cash on hand.

This range is based on certain assumptions, including that (i) all professional and college sports calendars that have been announced come to fruition, including the commencement of their 2020 to 2021 seasons, (ii) we continue to operate in states in which we are live today, and (iii) we do not launch operations in any new jurisdictions.

Recent Business Highlights

Near Term Initiatives

Earnings Conference Call and Webcast Details

RSI will host a conference call and audio webcast today at 5:00 p.m. Eastern Time (4:00 p.m. Central Time), during which management will discuss fourth quarter and full year results and provide commentary on business performance and its current outlook for 2021. A question-and-answer session will follow the prepared remarks.

The conference call may be accessed by dialing (844) 450-0390 for domestic callers or (236) 714-3032 for international callers. The conference call access code is 5695565.

A live audio webcast of the earnings conference call may be accessed on RSI’s website at ir.rushstreetinteractive.com, along with a copy of this press release and an investor slide presentation. The audio webcast and investor slide presentation will be available on RSI’s investor relations website until at least April 10, 2021.

About Rush Street Interactive

Founded in 2012 by gaming industry veterans, RSI is a market leader in online casino and sports betting in the U.S., currently operating real-money gaming in nine U.S. states. RSI launched its first online gaming site in New Jersey in September 2016, and through its BetRivers.com and PlaySugarHouse.com sites, RSI was the first to launch regulated online gaming in Colorado, Illinois, Indiana and Pennsylvania. RSI was named the 2020 Global Gaming Awards Digital Operator of the Year, and the 2020 EGR North America Awards Casino Operator of the Year and Customer Service Operator of the Year. RSI has been an early mover in Latin America and was the first U.S.-based gaming operator to launch a legal and regulated online casino and sportsbook, RushBet.co, in the country of Colombia. For more information, visit www.rushstreetinteractive.com.

Non-GAAP Financial Measures

In addition to providing financial measurements based on accounting principles generally accepted in the United States (“GAAP”), this press release includes certain financial measures that are not prepared in accordance with GAAP, including Adjusted EBITDA and Adjusted Operating Costs and Expenses, each of which is a non-GAAP performance measure that RSI uses to supplement its results presented in accordance with GAAP. A reconciliation of each such non-GAAP financial measure to the most directly comparable GAAP financial measure can be found below. RSI believes that presentation of these non-GAAP financial measures provides useful information to investors regarding RSI’s results of operations and operating performance, as they are similar to measures reported by its public competitors and are regularly used by security analysts, institutional investors and other interested parties in analyzing operating performance and prospects. These non-GAAP financial measures are not intended to be considered in isolation or as a substitute for any GAAP financial measures and, as calculated, may not be comparable to other similarly titled measures of performance of other companies in other industries or within the same industry.

RSI defines Adjusted EBITDA as net income (loss) before interest expense, income taxes, depreciation and amortization, share-based compensation, adjustments for certain one-time or non-recurring items and other adjustments. Adjusted EBITDA excludes certain expenses that are required in accordance with GAAP because certain expenses are either non-cash (for example, depreciation and amortization, and share-based compensation) or are not related to our underlying business performance (for example, interest income or expense).

RSI defines Adjusted Operating Costs and Expenses as RSI’s GAAP operating costs and expenses adjusted to exclude the impacts of share-based compensation, certain one-time or non-recurring items and other adjustments. Adjusted Operating Costs and Expenses excludes certain expenses that are required in accordance with GAAP because certain expenses are either non-cash (for example, share-based compensation) or are not related to our underlying business performance.

RSI includes these non-GAAP financial measures because management uses them to evaluate RSI’s core operating performance and trends and to make strategic decisions regarding the allocation of capital and new investments. Management believes that these non-GAAP financial measures provide investors with useful information on RSI’s past financial and operating performance, enable comparison of financial results from period-to-period where certain items may vary independent of business performance, and allow for greater transparency with respect to metrics used by RSI’s management in operating our business. Management also believes these non-GAAP financial measures are useful in evaluating our operating performance compared to that of other companies in our industry, as these metrics generally eliminate the effects of certain items that may vary from company to company for reasons unrelated to overall operating performance.

Key Metrics

RSI provides certain key metrics, including MAUs and ARPMAU, in this press release. RSI defines MAUs as the number of unique players per month who have placed at least one real-money bet across one or more of our online casino or online sports betting offerings, and it defines ARPMAU as average revenue for the applicable period divided by the average MAUs for the same period.

The numbers RSI uses to calculate MAUs and ARPMAU are based on internal RSI data. While these numbers are based on what RSI believes to be reasonable judgments and estimates of our customer base for the applicable period of measurement, there are inherent challenges in measuring usage and engagement with respect to our online offerings across our customer base. Such challenges and limitations may also affect RSI’s understanding of certain details of its business. In addition, RSI’s key metrics and related estimates, including the definitions and calculations of the same, may differ from estimates published by third parties or from similarly-titled metrics of its competitors due to differences in operations, offerings, methodology and access to information. RSI regularly reviews, and may adjust its processes for calculating, its internal metrics to improve their accuracy.

Forward-Looking Statements

This press release includes "forward-looking statements" within the meaning of the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995. RSI's actual results may differ from their expectations, estimates and projections and consequently, you should not rely on these forward-looking statements as predictions of future events. Words such as "expect," "estimate," "project," "budget," "forecast," "anticipate," "intend," "plan," "may," "will," "could," "should," "believes," "predicts," "potential," "continue," and similar expressions are intended to identify such forward-looking statements. These forward-looking statements include, without limitation, statements regarding guidance, RSI’s future results of operations or financial condition, RSI’s strategic plans and focus, player growth and engagement, product initiatives and the objectives of management for future operations. These forward-looking statements involve significant risks and uncertainties that could cause the actual results to differ materially from the expected results. Most of these factors are outside RSI's control and are difficult to predict. Factors that may cause such differences include, without limitation: changes in applicable laws or regulations; RSI’s ability to manage growth; RSI’s ability to execute our business plan and meet its projections; unanticipated product or service delays; general economic and market conditions impacting the demand for RSI’s products and services; economic and market conditions in the gaming, entertainment and leisure industry in the markets in which RSI operates; the potential adverse effects of the COVID-19 pandemic on capital markets, general economic conditions, unemployment and RSI’s liquidity, operations and personnel; and other risks and uncertainties indicated from time to time in RSI's filings with the SEC. RSI cautions that the foregoing list of factors is not exclusive. RSI cautions readers not to place undue reliance upon any forward-looking statements, which speak only as of the date made. RSI does not undertake or accept any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements to reflect any change in its expectations or any change in events, conditions or circumstances on which any such statement is based.

Media Contacts:

Jonathan Gasthalter / Carissa Felger / Nathaniel Garnick

(312) 319-9233 / (212) 257-4170

rsi@gasthalter.com

or

Lisa Johnson

(609) 788-8548

lisa@lisajohnsoncommunications.com

Investor Contact:

ir@rushstreetinteractive.com

Rush Street Interactive, Inc.

Consolidated Condensed Statements of Operations and Comprehensive Loss

(Unaudited and in thousands, except per share data)

Rush Street Interactive, Inc.

Reconciliations of GAAP to Non-GAAP Financial Measures

(Unaudited and in thousands)

Adjusted EBITDA:

Adjusted Operating Costs and Expenses:

¹ Previously disclosed one-time payment from affiliated casino.

² Share-based compensation.