a valve timing control system for an internal combustion engine which is capable of making an actual intake / exhaust valve timing resume speedily rapidly to a desired valve timing with high accuracy to thereby prevent degradation of exhaust gas quality includes a desired valve timing arithmetic means for determining desired valve timings for an intake valve and an exhaust valve , respectively , in dependence on an engine operation state , a variable valve timing mechanism for changing open / close timings of the valves , respectively , an actual valve timing detecting means for detecting actual valve timings , respectively , of the valves , an actual valve timing control means for generating a control quantity for the variable valve timing mechanism , and a learning means for learning a most retarded valve timing as a learned value . the detected value of the actual valve timing which is detected at a timing retarded more than the timing indicated by the learned value is reflected in the learned value in the course of operation of the engine .