The Moroccan has been frozen out by Gunners boss Arsene Wenger, who wanted the player to leave on a permanent deal, and will be available to make his Hammers debut next week
Goal.com revealed that the Hammers were interested in taking the Moroccan to Upton Park in December, although the Gunners would have preferred to shift the striker permanently.
|33/1||Arsenal are 33/1 with Bet365 to win the Champions League this season
Chamakh had trained at Arsenal's Colney base this morning before heading to east London to complete his temporary switch to the Hammers.
The former Bordeaux man is the Hammers' third signing of the winter window after Irish starlet Sean Maguire and returning midfielder Joe Cole.
Manager Sam Allardyce confirmed on Friday that Chamakh will not be able to make his debut for the Hammers in their FA Cup clash with Manchester United on Saturday.
Arsenal are keen to clear space in their squad and off their wage bill, with Goal.com also revealing that a formal approach has been made by the Gunners for Barcelona forward David Villa.
Goal.com also understands Arsene Wenger has made a £10 million bid for long-term transfer target Adrian Lopez of Atletico Madrid.