Buffett unveiled his (at)WarrenBuffett online handle on Thursday during a speech.
Buffett has always resisted investing in technology companies because he says he can't predict the future of those businesses the same way he can insurance or manufacturing.
Buffett says even though he may not understand Twitter well, he knows it can't be all bad because one of the company's co-founders is from Nebraska.
Buffett's first tweet said simply "Warren is in the house." By midday he had more than 32,000 followers.
Buffett doesn't have a computer in his office, but he uses one at home for research, writing and playing bridge online.
Follow Josh Funk online at www.twitter.com/funkwrite