In Triple-A with the Iowa Cubs in 2009, Fox had a breakout year. He was batting .423 and had hit 17 home runs and 50 RBIs by June 1, 2009, and was leading the PCL in both of these categories along with RBI, slugging percentage, and OPS. He was recalled to the Cubs on May 27, 2009. Fox was optioned back to Triple-A Iowa on June 10, 2009, and was recalled to the Chicago Cubs again on June 16. He achieved success as a part-time utility player, capable of filling in at corner outfield and infield positions, as well as catcher.