On June 27, 2011, Ramirez and teammate Carlos Peña homered twice in a 7–3 win over the Colorado Rockies. Ramirez and Pena both hit a two-run home run and a solo home run each.
On July 1, 2011, Ramírez hit his 300th career home run against the Chicago White Sox.
On July 10, 2011, Aramis Ramírez was asked by National League manager Bruce Bochy to replace Plácido Polanco in the All-Star Game, but Ramirez declined the invitation due to previous plans to be with his family during the break.
On October 30, 2011, Ramirez declined his portion of the $16 million option on his contract and chose to become a free agent.
On November 2, 2011, Ramirez was awarded the Louisville Slugger Silver Slugger Award for best offensive NL third baseman. In his ninth season as a Cub, Ramirez batted .306 with 35 doubles, 26 home runs and a team-high 93 RBIs. He also led the team in slugging percentage and on-base percentage.
On December 12, 2011, Ramirez signed a three-year deal worth $36 million with the Milwaukee Brewers.