The 29-year-old is looking forward to the challenge of playing in France after five years in England with Fulham.
"I was in a hurry to join Rennes," Bocanegra told the club's official website. "After five years with Fulham, I wanted to play in another European league other than England. I appreciate the French championship.
"It's a very high level and well reputed championship. The club also forms good players."