From Oct. 30 to Nov. 6, the famed venture capitalist and Facebook director went from holding almost 1.6 million Class A shares to just more than 750,000 in his charitable and living trusts, filings show. Andreessen's sales, in the time period directly surrounding Facebook earnings, were pursuant to an SEC rule that allows insiders to sell stock at a predetermined time, the filings said.
Facebook has 2.8 billion shares outstanding.
His venture capital firm, Andreessen Horowitz, and Facebook, both declined to comment to CNBC.
The social media giant reported third-quarter earnings Nov. 4, topping expectations for revenue, profit and monthly active users. Shares of Facebook are trading up almost 45 percent over the past year, and have hovered near 52-week highs since it reported results.
Andreessen's stock sold primarily between $102 and $110 over the two-week period. Shares of Facebook were around $108 midday Wednesday.
Correction: An earlier version of this story misstated Andreessen's Facebook ownership share.