On 30 January 2011, Keane joined West Ham United on loan for the remainder of the season. Keane made his debut for West Ham on 2 February in a 3–1 victory over Blackpool at Bloomfield Road, scoring his first goal in the process. West Ham had an option to extend the deal by two years if they avoided relegation from the Premier League. However, in May 2011 West Ham were relegated and Keane returned to Tottenham.
After playing for the newly reformed New York Cosmos in Paul Scholes's testimonial match, Keane joined LA Galaxy of Major League Soccer, becoming one of the club's three allowed designated players, alongside David Beckham and Landon Donovan. The Galaxy traded their previous third Designated Player, Juan Pablo Ángel, to city rivals Chivas USA to make room for Keane. He made his debut on 20 August 2011, in a California Clásico game against the San Jose Earthquakes, and scored his first goal for his new team in the 21st minute, in a 2–0 win at The Home Depot Center. On 13 September, he scored his first CONCACAF Champions League goal in a 2–1 group stage loss to Monarcas Morelia of Mexico.
The Galaxy finished the season as Western Conference champions, and won the Supporters' Shield. On 6 November, in his first full match, Keane scored in a 3–1 win over Real Salt Lake to book a place in the 2011 MLS Cup. Two weeks later, he assisted the winning goal for Donovan in the 72nd minute of the final as the Galaxy defeated Houston Dynamo 1–0 at their home stadium.
On 4 June 2011, Keane scored twice in a 2–0 away win against Macedonia in qualification for UEFA Euro 2012 to become the first Irish or British player to score more than 50 international goals. Following the game with Macedonia his total stood at 51 goals. He added another two goals in the Republic of Ireland's 4–0 play-off hammering of Estonia in Tallinn which effectively secured qualification for Euro 2012 in Poland and Ukraine to bring his goal tally to 53.