Hahn has filed to sell 147,999 shares, valued at $6.35 million, according to filings with the Securities and Exchange Commission.
Netscape's shares earlier this month spiked above $40 a share, but have since dropped to close at $36.38 yesterday, down 44 cents a share from Friday.
Hahn, who was named Netscape's chief technology officer in October 1997, stepped down last month to form the venture capital firm Inventures Group.
Via email, Hahn said he is selling shares he received under an employee stock option plan. He noted that he was required to sell the options within 90 days after leaving the company, and added that, if given a choice, he would not have sold.
Since leaving Netscape, Hahn has joined two companies as board members. Last month, he agreed to sit on the board of usenet provider Supernews and provide guidance on strategic planning and product development.
He also was appointed to the board of Kana Communications, a provider of Internet customer communications solutions. In that role, he will work with the management team in developing long-range product strategy and will provide operational advice.