The underwriters, led by Morgan Stanley, JPMorgan Chase & Co, Bank of America Merrill Lynch and Citigroup Inc, exercised their option on an additional 71.7 million shares worth $2.37 billion.
They also exercised their option to purchase 13 million shares of mandatory convertible junior preferred stock for $650 million, GM said on Friday.
The U.S. automaker last week raised $20.1 billion in an IPO of common and preferred shares in the biggest U.S. IPO ever. With this full overallotment, GM has now raised $23.1 billion, outpacing Agricultural Bank of China's $22.1 billion July IPO and making GM the biggest IPO globally.
The full overallotment exercise reflects strong demand for the stakes in the company.
Barclays Capital, Deutsche Bank, Goldman Sachs, Credit Suisse and Royal Bank of Canada are GM's other major underwriters. Lazard and Boston Consulting Group served as advisers to the Treasury. Evercore Partners advised GM.