A control system for an automatic transmission comprising: a first frictional engagement element (B-3) and a second frictional engagement element (B-2); a first hydraulic servo (28) for controlling the application/release of the first frictional engagement element (B-3) and a second hydraulic servo (29) for controlling the application/release of the second frictional engagement element (B-2); an oil passage (203) connected to the first hydraulic servo (28) for feeding/releasing an oil pressure to/from the first hydraulic servo (B-3); a regulator valve (25) disposed in the oil passage (203) for regulating the oil pressure in the oil passage (203); and signal pressure generating means (SLU) for applying a signal pressure to the regulator valve (25), whereby a predetermined gear stage is established by changing the grips of the first frictional engagement element (B-3) and the second frictional engagement element (B-2) by feeding/releasing the oil pressure to/from the first hydraulic servo (28) and the second hydraulic servo (29). The regulator valve (25) includes a valve member (250) having: a first pressure receiving area (A 3 ) to which is applied (256) a feed pressure to the first hydraulic servo (B-3) as a feedback pressure in a first direction; a second pressure receiving area (A 4 ) to which is applied the signal pressure (P SLU ) in a second direction opposite to the first direction; a fourth pressure receiving area (A 1 ) to which is applied a feed pressure to the second hydraulic servo (29) in the first direction at a grip-change shifting time when the first frictional engagement element (B-3) is released whereas the second frictional engagement element (B-2) is applied; and a third pressure receiving area (A 2 ) to which is applied the signal pressure in the second direction, for participating in the regulation of the oil pressure in the first oil passage only at the shifting time.