The 40-year-old had departed the club in June when his deal expired, but the Hammers have moved quickly to bolster their options between the posts following recent changes in the squad.
Fabianski originally arrived from Swansea City in 2018 and became a trusted figure during seven years at the London Stadium, making 216 appearances and keeping 55 clean sheets.
A reliable presence across multiple Premier League campaigns, he also played a key role in the side’s 2023 UEFA Europa Conference League triumph in Prague.
The Poland international’s (57 caps) return comes at a time when West Ham’s goalkeeping department has undergone major reshuffling.
The club invested £20 million in Leicester City’s Mads Hermansen during the summer, with the Dane starting all three of the Hammers’ league fixtures so far, recording one win and two defeats.
Meanwhile, French international Alphonse Areola was handed a start in the Carabao Cup last month but was unable to prevent a 3-2 defeat away to Wolverhampton Wanderers.
The Irons lost more depth this week when third-choice goalkeeper Wes Foderingham, who only joined on a free transfer in June, sealed a move to Cypriot outfit Aris Limassol.
That departure left new boss Graham Potter short of experienced cover, prompting West Ham to turn back to one of their most dependable former players.
Fabianski’s leadership and knowledge of the club could prove invaluable as the Hammers bid to bounce back from a disappointing 2024/25 season and secure one of the European places.
Hermansen remains the long-term number one.
However, the return of a fan favourite ensures West Ham have the reassurance of experience (376 Premier League apps) should they need it in the months ahead.
Stats from Transfermarkt