The French midfielder, who moved to Upton Park in September, expressed his delight at agreeing a new deal, which will take him through to the end of West Ham's first season at the Olympic Stadium.
"I am pleased," he told West Ham TV. "It's the culmination of a good year. We're always trying to do our best and so I'm very pleased to have signed for two more years.
"I think I've impressed the management, I know that I can always do better and I hope to do so. I'll give it my all as I have done in the first eight months.
"I've not had a chance to see the Olympic Stadium yet but apparently it's a very, very beautiful Stadium. So I'm very pleased to be a part of the project and I always want to please our fans, as much as possible."
Amalfitano, who marked his debut with a goal in September's 3-1 win over Liverpool, has featured in 22 matches this season.
He has not played since being sent off against former club West Brom last month, but is back from suspension and in the frame to play against Arsenal at the Emirates Stadium on Saturday.
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