Franco joined the Hammers on a free transfer as his contract at Villarreal expired earlier this summer.
“I am really happy to sign for West Ham. It was my dream to come to the Premier League and I am proud to play for a club that has so much history,” Franco told the club’s official website.
“This is a very important stage in my career and I hope to score lots of goals for the club this season and then play at the World Cup.
“This is an important team with great players and a great manager. I know that the club are very ambitious and want to do well. I want to do my best to make that happen and I am excited about the challenge.
“The main motivation was to play in the Premier League. I love English football and I love the Premier League.
“I had the possibility of joining Estudiantes and two Spanish clubs, but it was the Premier League that drew me here. I can fulfil my desire with West Ham and I am very happy to be here.”
