A hydraulic control apparatus for a vehicular fluid-actuated power transmitting device provided with a lock-up clutch and an oil cooler, the lock-up clutch being operable between an engaged state and a released state according to a difference between pressures of a working fluid in an engaging fluid chamber and a releasing fluid chamber, the oil cooler being connected to a fluid passage communicating with the engaging and releasing fluid chambers, and operable to cool the working fluid, the hydraulic control apparatus including an oil cooler by-pass valve operable to permit the working fluid to by-pass the oil cooler, and a low-temperature by-pass device operable to open the oil cooler by-pass valve, for permitting the working fluid to by-passes the oil cooler, when a temperature of the working fluid is lower than a predetermined lower limit.