On November 12, 2012, Cotts signed a minor league deal with an invitation to spring training to return to the Rangers organization. He failed to make the Rangers out of spring training in 2013 and rejoined Round Rock. He posted a 0.78 ERA with a 3–1 record and was promoted to the Rangers on May 21, 2013. After a nearly four-year absence from the Major Leagues, he threw six pitches against Oakland on May 21. His agent Joe Bick said, "When he went back to the mound that first time, I had a lump the size of a softball in my throat." He said of his return to the Major Leagues, "There's a point where you go through all of it where you don't know if you're ever going to play again; I never was really accepting of that." He became a left-handed specialist for the Rangers bullpen. However, he had better platoon splits against right-handed batters than left-handed batters after joining the Rangers. In 2013, he held opposing right-handed batters to a .436 on-base plus slugging (OPS) percentage while left-handed hitters had a .565 OPS.