A control system for an automatic transmission having a transmission gear mechanism and a plurality of friction coupling elements which are selectively locked and unlocked with hydraulic oil to change power transmission paths to place the automatic transmission into desired available gears, a first one of the friction coupling elements having a locking pressure chamber and an unlocking pressure chamber and being locked when operating oil is supplied into only the locking pressure chamber and unlocking when operating oil is coincidentally supplied into the locking pressure chamber and the unlocking pressure chamber, and a second one of the friction coupling elements having a locking/unlocking pressure chamber in communication, with the unlocking pressure chamber of the first friction coupling element and being locked only when operation oil is supplied into the locking/unlocking pressure chamber. The control system includes a transition level control for controlling a pressure level of transitional pressure of operating oil increasing in pressure level while being supplied to the locking/unlocking pressure chamber of the second friction coupling element during a first specified gear shift with a first friction coupling element and the second friction coupling element are simultaneously unlocked and locked, respectively, and decreasing while being discharged from the locking/unlocking pressure chamber of the second friction coupling element during a second specific gear shift wherein the first friction coupling element and the second friction coupling element are simultaneously locked and unlocked, respectively, and a transitional duration control for controlling a duration time of the transitional pressure during any one of the first and second specific gear shifts.