A hydraulic control system of an automatic transmission for a hybrid vehicle provides for simplifying structure of a valve body and improving responsiveness as a consequence of directly controlling hydraulic pressure supplied to friction elements. The hydraulic control system may operate first and second clutches and first and second brakes selectively according to each driving mode, and may include: a first proportional control solenoid valve for selectively supplying forward pressure and reverse pressure supplied from a manual valve to the first clutch; a second proportional control solenoid valve for selectively supplying line pressure supplied from a primary regulator valve to the second clutch; a third proportional control solenoid valve for selectively supplying the line pressure supplied from the primary regulator valve to the first brake; and a fourth proportional control solenoid valve for selectively supplying the forward pressure supplied from the manual valve to the second brake.