There had been doubts as to whether the 35-year-old would remain a Hammer beyond the end of this campaign, as his contract was due to expire in the summer.
The retention of the stopper comes after club legend and long-standing captain Mark Noble announced he would remain at the club for one final season.
Fabianski has played 25 times in the Premier League this season, conceding 29 goals in the process as the Irons go in pursuit of Champions League qualification.
Whether the Pole can retain his place as the out and out number one next term is another question.
At 35, and with the Irons potentially competing in Europe next season, David Moyes could still look to make additions to the goalkeeping department this summer.
There have already been a plethora of names mentioned in passing with filling what looked to be an impending goalkeeping void at the London Stadium, with Sheffield United ‘keeper Aaron Ramsdale the latest to be linked.