Zuckerberg would be eligible to sell his 444 million Facebook shares on or after Oct. 29, when the sales moratorium on his shares ends.
Ending the so-called lockup period, which was put in place to prevent a chaotic dumping of shares, was staggered for early Facebook shareholders, and some notable investors got out quickly after their lockup periods ended, CNN reported Wednesday.
With the value of Facebook shares dropping 54 percent since May, when the company went public, investor Peter Thiel sold his entire Facebook holdings in August, soon after his lockup period ended.
Even Facebook co-founder Dustin Moskovitz sold shares a few days after his lockup period ended.
Zuckerberg, who has an option to purchase 60 million more shares, sold a large portion of his holdings during the company's initial public offering.
The shares were sold to pay a huge tax bill. But it may have contributed to the unease about the company, given the most famous of its founders was reducing his shares in the company.
When Zuckerberg's decision to keep his shares became public, the company's stock went up about 2 percent.
In the regulatory filing, Facebook said it would convert restricted shares -- a category of shares held by most staff members -- to common shares that can be sold on Oct. 29, about two weeks earlier than previously planned.
By doing so, employees can begin to sell their shares earlier and figure out how to cover their tax bills, which will also be sizable this year.