The signing comes three months after former Manchester United defender kicked a fan in the head in France and was subsequently sacked by Marseille.
He reunites with his former United manager David Moyes in east London.
“It happened really fast,” said Evra. “My agent called me and told me I needed to come back [from Dubai] to London as quick as I could and I had a nice meeting with the manager, who I know from Manchester United, of course, and I met the Chairman, so it was really easy.
“When you have to make a deal and money is not the issue, the deal could be done in five minutes. The main thing was for me to join West Ham and to help my teammates to win as many games as we can.
“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!”
“I’m really happy to be a Hammer, to be back in the Premier League and I love this game!
“It’s amazing to be back and I am thankful to West Ham for giving me the opportunity to do my job.
“When I wake up and know I am going to work hard, to have fun with my teammates and give my best on the pitch, I want to say a massive thanks to West Ham, to the Chairman, to the manager to all my teammates, who have given me a nice welcome, my agent and my brother.