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Filed Pursuant to Rule 433
Issuer Free Writing Prospectus
Relating to Preliminary Prospectus dated April 20, 2010
Registration No. 333-164590

Douglas Dynamics, Inc.

        This free writing prospectus of Douglas Dynamics, Inc. relates only to the offering of its common stock described in, and should be read together with, the revised preliminary prospectus dated April 29, 2010 (the "Preliminary Prospectus"), included in Amendment No. 6 to the Registration Statement on Form S-1 (File No. 333-164590). The Preliminary Prospectus included in Amendment No. 6 to the Registration Statement can be accessed through the following link: http://www.sec.gov/Archives/edgar/data/1287213/000104746910004460/a2198387zs-1a.htm

        This free writing prospectus is only a summary of the changes included in the Preliminary Prospectus included in Amendment No. 6 to the Registration Statement and should be read together with the Preliminary Prospectus, including the section entitled "Risk Factors" beginning on page 14 of the Preliminary Prospectus. Capitalized terms used, but not defined, herein have the meanings set forth in the Preliminary Prospectus.

        This free writing prospectus reflects the following supplements and updates included in the Preliminary Prospectus.

1.

The disclosure set forth on page 3 of the Preliminary Prospectus in the second sentence of the first paragraph under "Prospectus Summary — Our Competitive Strengths" has been updated to read as follows:

        As the market leader in snow and ice control equipment for light trucks, we enjoy a set of competitive advantages versus smaller, more regionally focused equipment providers, which allows us to generate robust cash flows in all snowfall environments and to support continued investment in our products, distribution capabilities and brand regardless of annual volume fluctuations.

2.

The disclosure set forth on page 8 of the Preliminary Prospectus in the first sentence under "The Offering — Dividend Policy" has been updated to read as follows:

        Our Board of Directors will adopt a dividend policy, effective upon the consummation of this offering, that reflects an intention to distribute to our stockholders a regular quarterly cash dividend, commencing during the first full fiscal quarter following the consummation of this offering in equal quarterly installments at an initial annual rate of $0.78 per share.

3.

The disclosure set forth on pages 17-18 of the Preliminary Prospectus under "Risk Factors — We face competition from other companies in our industry, and if we are unable to compete effectively with these companies, it could have an adverse effect on our sales and profitability" has been updated to read as follows:

We face competition from other companies in our industry, and if we are unable to compete effectively with these companies, it could have an adverse effect on our sales and profitability. Price competition among our distributors could negatively affect our market share.

        We primarily compete with regional manufacturers of snow and ice control equipment for light trucks. While we are the most geographically diverse company in our industry, we may face increasing

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competition in the markets in which we operate. In saturated markets, price competition may lead to a decrease in our market share or a compression of our margins, both of which would affect our profitability. Moreover, current or future competitors may grow their market share and develop superior service and may have or may develop greater financial resources, lower costs, superior technology or more favorable operating conditions than we maintain. As a result, competitive pressures we face may cause price reductions for our products, which would affect our profitability or result in decreased sales and operating income. Additionally, the potential for saturation of the markets in which we compete or channel conflicts among our brands and shifts in consumer preferences may increase these competitive pressures or may result in increased competition among our distributors and affect our sales and profitability. In addition, price competition among the distributors that sell our products could lead to margin erosion among our distributors, which could in turn result in compressed margins or loss of market share for us. Management believes that after Douglas, the next largest competitors in the market for snow and ice control equipment for light trucks are BOSS and Meyer, respectively, and accordingly represent our primary competitors for market share.

4.

The disclosure set forth on page 28 of the Preliminary Prospectus in the first sentence of Footnote (1) to the table set forth under "Use of Proceeds" has been updated to read as follows:

(1)

Includes approximately $0.6 million of proceeds due to the voluntary repayment upon the consummation of this offering of a portion of certain loans to former management.

5.

The disclosure set forth on page 29 of the Preliminary Prospectus in the second paragraph under "Dividend Policy and Restrictions" has been updated to read as follows:

        In accordance with this dividend policy and based upon our Board of Directors' review of our historical results of operations and the restrictions in our debt instruments, we currently intend to pay a quarterly dividend on our common stock, commencing during the first full fiscal quarter following the consummation of this offering in equal quarterly installments at an initial annual rate of $0.78 per share.

6.

The disclosure set forth on page 60 of the Preliminary Prospectus in the third sentence of the first paragraph under "Business — Competitive Strengths" has been updated to read as follows:

        As the market leader, we enjoy a set of competitive advantages versus smaller, more regionally focused equipment providers, which allows us to generate robust cash flows in all snowfall environments and to support continued investment in our products, distribution capabilities and brand regardless of annual volume fluctuations.

7.

The disclosure set forth on page 61 of the Preliminary Prospectus in the fifth sentence under "Business — Competitive Strengths — Exceptional Customer Loyalty and Brand Equity" has been updated to read as follows:

        Because a professional snowplower can typically recoup the cost of a plow within a very short period of time, and in some cases, as a result of one major snowfall event, we believe quality, reliability and functionality are more important factors in our end-users' purchasing decisions and further believe that our end userprofessional snowplowers are often willing to pay a premium price for reputable products that include these premium features.

8.

The disclosure set forth on pages 65-66 of the Preliminary Prospectus under "Business — Business Strategy — Snow and Ice Control Equipment" has been updated to include the following information after the second sentence of the third paragraph:

        The revenue and gross profit derived from our sales of sand and salt spreaders constitute less than

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10% of our total revenue and gross profit. The current retail prices of our sand and salt spreaders generally range from approximately $1,600 to $11,500. Notwithstanding the minor distinctions noted above, we believe nearly all of the products sold under the WESTERN® and FISHER® brands are identical or practically identical to one another (with the only differences generally being cosmetic). Further, the Company's BLIZZARD® product line generally consists of a subset of the products sold under the WESTERN® and FISHER® names, with relatively minor cosmetic differences.

9.

The disclosure set forth on page 78 of the Preliminary Prospectus in the last paragraph under "Management and Board of Directors — Structure of our Board of Directors" has been updated to include the following information at the end of such paragraph:

        In accordance with the listing standards of the NYSE, within twelve months of the listing of our shares on the NYSE, we plan to appoint at least two independent members to replace two non-independent members so that a majority of our Board of Directors will be independent within the meaning of the listing standards of the NYSE.

10.

The disclosure set forth on page 92 the Preliminary Prospectus in the last paragraph under "Executive Compensation — Narrative Disclosure to Summary Compensation Table for Year Ended December 31, 2009 and Grants of Plan-Based Awards in Year 2009 Table" has been updated to read as follows:

        Prior to the consummation of this offering, each of these employment agreements will be amended for purposes of complying with Section 409A of the Internal Revenue Code. These amendments provide that it is our intent that the agreements satisfy the requirements of Section 409A and are interpreted consistent with that intent. The amendments further provide that, to the extent required by Section 409A, severance payments that become due under the agreements that are considered deferred compensation at the time of termination of employment will be delayed until the earlier of six months following the applicable executive's termination of employment or the date of the executive's death following termination of employment, at which time all such delayed payments will be paid in lump sum to the executive without interest.

11.

The disclosure set forth on page 103 of the Preliminary Prospectus in the fifth paragraph under "Principal and Selling Stockholders" has been updated to read as follows:

        Each of the selling stockholders, other than our former managers and those who will be acquiring shares pursuant to the exercise of outstanding stock options immediately prior to the consummation of this offering, acquired their respective shares of our common stock from the Aurora Entities in 2004 following the Acquisition at a price of $4.21 per share. Our former managers acquired their shares of common stock upon exercise of stock options, granted in 2004, at an exercise price of $4.21 per share, from 2006 to 2007. Other than Messrs. Janik, McCormick and Adamson, our selling stockholders who hold stock options were granted those options in 2005. Messrs. Janik and McCormick were granted their stock options in 2004 and Mr. Adamson was granted his stock options in 2007. Each of our outstanding stock options bear an exercise price of $4.21 per share.

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12.

The table set forth on page 104 of the Preliminary Prospectus under "Principal and Selling Stockholders" has been updated to read as follows:

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14.

The disclosure set forth on pages 109-110 of the Preliminary Prospectus in the first and second bullet points under "Certain Relationships and Related Party Transactions — Related Party Transactions — Promissory Notes/Pledge and Security Agreements" has been updated to include the following information for Messrs. Smitsdorff and Roethle, respectively:

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Mr. Smitsdorff has voluntarily agreed to apply a portion of the proceeds from the sale of a portion of his shares in this offering towards the repayment of the promissory notes.

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•

Mr. Roethle has voluntarily agreed to apply a portion of the proceeds from the sale of a portion of his shares in this offering towards the repayment of the promissory notes.

15.

The disclosure set forth on page F-4 of the Preliminary Prospectus has been updated to include the following information:

16.

The disclosure set forth on page F-7 of the Preliminary Prospectus has been updated under "Note 2 — Summary of Significant Accounting Policies" to include the following information after the section entitled "Principles of consolidation":

Unaudited pro forma net income (loss) per common share and weighted average common shares outstanding

        The pro forma basic and diluted net income (loss) per common share and pro forma basic and diluted weighted average shares are unaudited and give effect for all periods to the 23.75 for 1.00 stock split of the Company's common stock to occur immediately prior to the completion of this offering.

17.

The disclosure set forth on page F-31 of the Preliminary Prospectus has been updated under "Note 14 — Earnings Per Share" to include the following information at the end of such note:

        The following reflects the pro forma weighted average shares that were used to calculate pro forma basic and diluted earnings per share as a result of the 23.75 for 1.00 stock split of the Company's common stock to occur immediately prior to the completion of this offering:

THE ISSUER HAS FILED A REGISTRATION STATEMENT (INCLUDING A PRELIMINARY PROSPECTUS) WITH THE SEC FOR THE OFFERING TO WHICH THIS COMMUNICATION RELATES. BEFORE YOU INVEST, YOU SHOULD READ THE PRELIMINARY PROSPECTUS IN THAT REGISTRATION STATEMENT AND THE OTHER DOCUMENTS THE ISSUER HAS FILED WITH THE SEC FOR MORE COMPLETE INFORMATION ABOUT THE ISSUER AND THE OFFERING. YOU MAY GET THESE DOCUMENTS FOR FREE BY VISITING EDGAR ON THE SEC'S WEBSITE AT HTTP://WWW.SEC.GOV. ALTERNATIVELY, THE ISSUER, ANY UNDERWRITER OR ANY DEALER PARTICIPATING IN THE OFFERING WILL ARRANGE TO SEND YOU A PROSPECTUS IF YOU REQUEST IT BY CALLING CREDIT SUISSE AT (800) 221-1037.

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Filed Pursuant to Rule 433 Issuer Free Writing Prospectus Relating to Preliminary Prospectus dated April 20, 2010 Registration No. 333-164590