The Eagles pulled the trigger after a dreadful run of just one win in their last 14 Premier League matches.
Palace now find themselves in a battle for top-flight survival following Tuesday's defeat at rivals Brighton.
And the hunt is already underway for Vieira's replacement. As well as the Frenchman, the Londoners have also parted ways with coaches Osian Roberts, Kristian Wilson and Said Aigoun.
Chairman Steve Parish said as cited by Sports Central: “It is with enormous regret that this difficult decision has been made. "Ultimately, results in recent months have placed us in a precarious league position and we felt a change is necessary to give us the best chance of retaining Premier League status. "That said, Patrick’s impact since joining us in the summer of 2021 has been significant, and he is held in the highest regard by myself, and all of his colleagues.
He added: "He led the team to a Wembley FA Cup semi-final and respectable 12th placed finish last season playing some exciting football, which was a challenging and crucial campaign for the club given the changes we made to the squad prior to his arrival. "Patrick has given his all to the club, and we all thank him and his team for their service. “We also wish Patrick, Osian, Kristian and Said the very best for their futures.
Vieira took charge of 65 Premier League matches with the Eagles and had a 26 per cent win ratio.
Fans had mixed feelings about the sacking, with one calling it a "real shame".
Another said: "What is the actual point of sacking him now with about 10 games to go?"
While one wrote: "Thank you Patrick but this was the time to go."
Former Palace star Clinton Morrison this week warned results were not good enough.
He said: "The noises at Selhurst Park from the fans, they’re not happy, obviously, with the results. "The performances have been good, but it is not being clinical enough. “We say season upon season with the club: can they get a centre forward who could score them 10-15 goals? “They have evolved… they do try to dominate the football now & create chances, which Patrick implemented, but they’re not clinical enough. It’s the same old story.
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