Disclosed are an apparatus for adjusting temperature of oil for a vehicle, and a method for controlling the apparatus. The apparatus includes an EGR valve installed on a fluid channel branching off from an exhaust pipe, a complex heat exchanger structured to transfer exhaust gas having passed through the EGR valve to an engine intake pipe via an EGR cooling path in which the exhaust gas having passed through the EGR valve performs heat exchange with coolant, an oil heating path in which the exhaust gas having passed through the EGR valve performs heat exchange with oil, and a bypass path in which the exhaust gas having passed through the EGR valve does not perform heat exchange, an NOx sensor installed in the exhaust pipe, and a controller that controls the complex heat exchanger in response to a signal from the NOx sensor.