Evra was subsequently banned from European competitions by UEFA for the rest of the season but he will be able to play domestically for West Ham.
"It's amazing to be back (in England) and I am thankful to West Ham for giving me the opportunity to do my job," Evra told the club's website (www.whufc.com).
"When I wake up and know I am going to work hard, to have fun with my team mates and give my best on the pitch, I want to say a massive thanks to West Ham, to the Chairman, to the manager and to all my team mates."
Evra made 379 appearances for United between 2006 and 2014 and won nine major trophies, including five Premier League titles and the Champions League in 2008.
He previously played for West Ham boss David Moyes when he was in charge at Old Trafford during the 2013-14 season.
"I had a nice meeting with the manager, who I know from Manchester United, of course... so it was really easy," Evra added.
"It was the fastest thing I have done in my life, because both parties wanted to work together, so it was very easy to make an agreement."
Evra left United to join Juventus in 2014, and won two Serie A titles before securing a moving to Marseille.
He made nine appearances for the French club this season, most recently in October, before the incident prior to a European fixture at Portugal's Vitoria Guimaraes ended his stint abruptly.
West Ham are 12th in the league but only three points off the relegation places. It's possible that Evra, capped 81 times by France, could make his debut for the club in their Premier League fixture at home to Watford on Saturday.
(Reporting by Hardik Vyas in Bengaluru; Editing by Christian Radnedge)
