Mr Mason bid farewell in a note to his employees and Twitter followers with his customary humour.
“After four and a half intense and wonderful years as CEO of Groupon, I’ve decided that I’d like to spend more time with my family,” he wrote. “Just kidding – I was fired today.”
After ending Thursday’s session down 24 per cent, Groupon shares rose as much as 13 per cent in after-hours trading on news of Mr Mason’s departure.
Mr Mason’s exit reveals a split in the company that he founded with Eric Lefkofsky and Brad Keywell.
Together, the three men share majority voting power on Groupon’s board. Mr Mason holds 20 per cent of the voting rights, Mr Lefkofsky controls 28 per cent, and Mr Keywell has 10 per cent.
Since its IPO in November 2011, shares in Groupon have tumbled from a high of $26 to $4.53 at Thursday’s close.
The company did not provide details on how the decision on Mr Mason’s departure was reached.
“On behalf of the entire Groupon board, I want to thank Andrew for his leadership, his creativity and his deep loyalty to Groupon,” Mr Lefkofsky said.
Mr Mason will retain his Groupon shares and his voting rights, but he has resigned from the board.
A search for a new chief executive has begun. In the interim, Mr Lefkofsky and fellow board member Ted Leonsis will serve as co-leaders in a shared post Groupon is calling “office of the chief executive”.
Under Mr Mason’s watch, Groupon made several missteps as both a private and public company, including backtracking on a controversial accounting approach set out in its initial IPO filing, and later revising its revenues after failing to reserve enough for refunds.
He was known for pointing to his advisers for giving him bad advice in the past, but on Thursday he shouldered the responsibility.
“The events of the last year and a half speak for themselves. As CEO, I am accountable.”