The purchase is significant because the financial health of the auto industry has been central to President Obama's argument for reelection.
The federal government loaned GM $6.7 billion from the Troubled Asset Relief Program (TARP) in 2008 and 2009, and purchased $50 billion of the company's stock, leading some conservatives to derisively refer to the company as "Government Motors."
GM has reported that it made a profit of $7.6 billion last year, a record for the company, and Obama has argued that the turnaround of the company proves he is best suited to continue led the economy after November's election.
Critics of the bailouts often counter that the federal government still owns a large percentage of GM's shares.
Buffett is one of the wealthiest people in the world, and he is no stranger to being a political figure after his comments about the fairness of the U.S. tax system led Obama to dub his proposal to increase rates on top wage earners the "Buffett Rule."
Republicans have criticized Buffett for suggested that people like him should pay higher taxes, arguing that he could easily send more money to the federal government.
In addition to his purchase of General Motors shares, Buffett's firm reportedly purchased a large group of U.S. newspapers from Media General.