"It's official. Now Chris Horner is a Lampre Merida rider," Lampre-Merida wrote on their Twitter feed.
The 42-year-old Horner won the 2013 Vuelta, becoming the oldest grand tour winner, but his contract with RadioShack -- now Trek Factory Racing -- was not renewed.
His previous best performance in a grand tour was ninth in the 2010 Tour de France.
Horner joins world champion Rui Costa of Portugal at Lampre, who finished 14th in the 19-team strong World Tour last year.