UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

(Amendment No. 1)

(Mark One)

For the fiscal year ended May 28, 2005

OR

For the transition period from                      to                    

Commission File Number: 0-12906

RICHARDSON ELECTRONICS, LTD.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (630) 208-2200

Securities registered pursuant to Section 12(b) of the Act: None

Securities registered pursuant to Section 12(g) of the Act: Common Stock, $0.05 Par Value

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.

x  Yes    ¨  No

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.

x

Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Exchange Act).

x  Yes    ¨  No

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).

¨  Yes    x  No

The aggregate market value of the registrant’s common stock held by non-affiliates of the registrant as of November 27, 2004, was approximately $153,700,000.

As of November 14, 2005, there were outstanding 15,644,457 shares of Common Stock, $.05 par value, inclusive of 1,328,961 shares held in treasury, and 3,109,697 shares of Class B Common Stock, $.05 par value, which are convertible into Common Stock of the registrant on a share for share basis.

TABLE OF CONTENTS

EXPLANATORY NOTE

Richardson Electronics, Ltd. is filing this Form 10-K/A to amend Part II, Item 9A(e) of the Annual Report filed on Form 10-K for the fiscal year ended May 28, 2005, which was previously filed with the Securities and Exchange Commission on August 26, 2005 (the “Form 10-K”), to solely correct the Report of Independent Registered Public Accounting Firm which contained a typographical error. The following paragraph was inadvertently omitted from the Report of Independent Registered Public Accounting Firm:

“We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States), the consolidated balance sheets of Richardson Electronics, Ltd. and subsidiaries as of May 28, 2005 and May 29, 2004, and the related consolidated statements of operations, stockholders’ equity and comprehensive income (loss), and cash flows for each of the years in the two-year period ended May 28, 2005. The aforementioned material weaknesses were considered in determining the nature, timing, and extent of audit tests applied in our audit of the May 28, 2005 consolidated financial statements, and this report does not affect our report dated August 26, 2005, which expressed an unqualified opinion on those consolidated financial statements.”

In connection with the filing of this Form 10-K/A and pursuant to Rules 12b-15, 13a-14(a) and 13(a)-14(b) under Exchange Act, Richardson Electronics Ltd. is including currently dated certifications. Except as described above, no other amendments are being made to the Form 10-K. This Form 10-K/A does not reflect events occurring after the filing of Form 10-K or modify or update the disclosure contained therein in any way other than as required to reflect the amendments discussed above.

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PART II

(e) Report of Independent Registered Public Accounting Firm

The Board of Directors and Stockholders

Richardson Electronics, Ltd.:

We have audited management’s assessment, included in the accompanying Management’s Report on Internal Control over Financial Reporting (Item 9A.(b)), that Richardson Electronics, Ltd. and subsidiaries (the Company) did not maintain effective internal control over financial reporting as of May 28, 2005, because of the effect of material weaknesses identified in management’s assessment, based on criteria established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO). Richardson Electronics, Ltd.’s management is responsible for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting. Our responsibility is to express an opinion on management’s assessment and an opinion on the effectiveness of the Company’s internal control over financial reporting based on our audit.

We conducted our audit in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether effective internal control over financial reporting was maintained in all material respects. Our audit included obtaining an understanding of internal control over financial reporting, evaluating management’s assessment, testing and evaluating the design and operating effectiveness of internal control, and performing such other procedures as we considered necessary in the circumstances. We believe that our audit provides a reasonable basis for our opinion.

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

A material weakness is a control deficiency, or combination of control deficiencies, that results in more than a remote likelihood that a material misstatement of the annual or interim financial

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statements will not be prevented or detected. The following material weaknesses have been identified and included in management’s assessment as of May 28, 2005:

These deficiencies resulted in a more than remote likelihood that a material misstatement of the Company’s annual or interim financial statements would not be prevented or detected, and contributed to the development of other material weaknesses described below.

As a result of these deficiencies, material misstatements were identified in the Company’s deferred tax assets and liabilities, valuation allowance, and tax reserves.

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As a result of these deficiencies, misstatements were identified in the Company’s consolidated financial statements. These deficiencies in internal control over financial reporting resulted in a more than remote likelihood that a material misstatement of the Company’s interim or annual financial statements would not be prevented or detected.

This deficiency resulted in material errors in accounting which required restatement of the Company’s consolidated financial statements as of and for the years ended June 1, 2002 and May 31, 2003 and for interim periods in 2003 and 2004 and the first and second quarters of fiscal 2005 to reflect the correction of these errors in accounting.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States), the consolidated balance sheets of Richardson Electronics, Ltd. and subsidiaries as of May 28, 2005 and May 29, 2004, and the related consolidated statements of operations, stockholders’ equity and comprehensive income (loss), and cash flows for each of the years in the two-year period ended May 28, 2005. The aforementioned material weaknesses were considered in determining the nature, timing, and extent of audit tests applied in our audit of the May 28, 2005 consolidated financial statements, and this report does not affect our report dated August 26, 2005, which expressed an unqualified opinion on those consolidated financial statements.

In our opinion, management’s assessment that Richardson Electronics, Ltd. and subsidiaries did not maintain effective internal control over financial reporting as of May 28, 2005, is fairly stated, in all material respects, based on criteria established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO). Also, in our opinion, because of the effect of the material weaknesses described above on the achievement of the objectives of the control criteria, Richardson Electronics, Ltd. and subsidiaries have not maintained effective internal control over financial reporting as of May 28, 2005, based on criteria established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

/s/ KPMG LLP

Chicago, Illinois

August 26, 2005

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PART IV

(a) Exhibit

See Exhibit Index.

(b) Financial Statement Schedules

None

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SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

RICHARDSON ELECTRONICS, LTD.

Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

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Exhibit Index

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