A shift control system for an automatic transmission. The shift control system includes an oil temperature sensor, a hydraulic controller to operate a hydraulic clutch, and a control unit in operative communication with the oil temperature sensor and the hydraulic controller. When a gear shift is requested just after an engine restart, the control unit controls the hydraulic clutch with an adjusted shift control process, in contrast to a normal condition of the engine. This adjustment is determined based on a first oil temperature at a time point when the engine is last stopped and on a temperature difference between the first oil temperature and a second oil temperature at a time point when the engine is last restarted after the last engine stop.