A control system for an automatic transmission that does not require a cut-off valve, and that can inhibit a reverse control even if a detection unit for detecting a shift range fails. The control system includes a first friction engagement element, which is engaged in predetermined forward and reverse shift speeds, a detection unit that detects a shift range from shift ranges that include a forward range and a reverse range; a failure judgment unit for judging failure of the detection unit, and an avoidance unit for shifting to a forward shift speed that does not engage the first friction engagement element if the failure judgment unit determines that the detection unit has failed.