"I don't hold any of my Twitter shares anymore -- except to the extent they are represented in index funds," Ballmer said on CNBC's "Halftime Report."
Ballmer, now the owner of the Los Angeles Clippers basketball team, first tweeted that he accumulated the stake back in October of 2015. Around that time, he acquired about a 4 percent stake in Twitter with shares north of $25 per share.
He said he sold his Twitter shares at "the recent high," suggesting it was around the time when Twitter last reached around $33 to $35. Twitter last closed at a high of $36.60 on March 14, and last closed above $33 per share on March 19.
Although no longer a major shareholder, Ballmer still believes in the company.
"I think Twitter will succeed and it will move forward, but I simplified my life and I got out at a very nice price. I sold really because I decided investing money is not my business," Ballmer said. "I'm in index funds, I'm in Microsoft — it keeps my life simpler."
Shares of Twitter fell as much as 1 percent on the day, and are up 23 percent year-to-date.
-CNBC's Chloe Aiello contributed to this story.