Massive CEO, Mitch Davis, and president of new media, Nichola Longano, will both leave the the in-game ads specialist this month.
The company was bought by Microsoft in May last year to bring ads to the Xbox 360, and apply Massive technology to services such as Windows Live and MSN.
No reason was given for the departure of the two executives.
"Pursuing entrepreneurial start-ups has been my passion," said Davis in a statement. "Massive is well-positioned in the in-game advertising industry, and I look forward to watching future growth from outside the company as I move on to pursue new interests outside of Massive and Microsoft."