The out-of-favor Moroccan joins West Ham for the remainder of the season and will be available to make his Hammers debut next week.
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.
Chamakh has fallen out of favor at Arsenal, making just four appearances all season, none of which came in league play. He scored two goals in League Cup action and also played in one UEFA Champions League match.