Berkshire's total investment was $256.6 million. The publicly owned investment firm's stake in GM is the 20th largest of all shareholders, according to Bloomberg. By comparison, the federal government owns more than 500 million shares.
Buffett likes to invest big in companies he sees as undervalued, though the GM buy is on the small side for the investor nicknamed the Oracle of Omaha. It could mean another Berkshire associate approved the trade.
"It confirms the investment thesis that we've had on GM," said Morningstar analyst Richard Hilgert. "We definitely see some value there, just as Mr. Buffett does, and hopefully this will draw a little more attention to the stock from investors."
GM's stock closed down less than 1% Tuesday at $21.42, but rose nearly 4% in after-hours trading. GM shares were priced at $33 during the company's initial public offering in November 2010 after emerging from bankruptcy.
A Berkshire spokeswoman was not available Tuesday. And GM spokesman Jim Cain declined to comment.