EXHIBIT 5./EXHIBIT 23.1 Opinion of Thacher Proffitt & Wood, counsel for Registrant, as to the legality of the securities being registered Consent of Thacher Proffitt & Wood Writer's Direct Dial: 212-912-7435 E-mail: ebright@thacherproffitt.com November 14, 2000 Haven Bancorp, Inc. 615 Merrick Avenue Westbury, New York 11590 Re: 1993 Incentive Stock Option Plan and 1993 Stock Option Plan for Outside Directors -------------------------------------------- Ladies and Gentlemen: We have acted as counsel for Haven Bancorp, Inc., a Delaware corporation ("Corporation"), in connection with the filing of a registration statement on Form S-8 under the Securities Act of 1933, as amended ("Registration Statement"), with respect to 69,430 shares of its common stock, par value $.01 per share ("Shares"), which may be issued pursuant to the Haven Bancorp, Inc. 1993 Incentive Stock Option Plan, as amended, and 29,754 Shares, which may be issued pursuant to the Haven Bancorp, Inc. 1993 Stock Option Plan for Outside Directors, as amended. In rendering the opinion set forth below, we do not express any opinion concerning law other than the federal law of the United States and the corporate law of the States of New York and Delaware. We have examined originals or copies, certified or otherwise identified, of such documents, corporate records and other instruments as we have deemed necessary or advisable for purposes of this opinion. As to matters of fact, we have examined and relied upon the Plans described above and, where we have deemed appropriate, representations or certificates of officers of the Corporation or public officials. We have assumed the authenticity of all documents submitted to us as originals, the genuineness of all signatures, the legal capacity of natural persons and the conformity to the originals of all documents submitted to us as copies. Based on the foregoing, we are of the opinion that the Shares which are being registered pursuant to the Registration Statement have been duly authorized and, when issued and paid for in accordance with the terms of the Plans, such Shares will be validly issued, fully paid and non-assessable. Haven Bancorp, Inc. November 14, 2000 Page 2. In rendering the opinion set forth above, we have not passed upon and do not purport to pass upon the application of "doing business" or securities or "blue-sky" laws of any jurisdiction (except federal securities law). This opinion is given solely for the benefit of the Corporation and purchasers of shares under the Plans, and no other person or entity is entitled to rely hereon without express written consent. We hereby consent to the filing of this opinion as an exhibit to the Registration Statement and to the references to our Firm's name therein. Very truly yours, THACHER PROFFITT & WOOD By:/s/ W. Edward Bright ---------------------- W. Edward Bright