The occurrence of defects is unavoidable during the service of tapered roller bearings (TRBs). Unfortunately, there is little information available in the literature about the mechanisms of effects of the defect on roller-raceways’ contact states and friction torque of tapered roller bearings. The present study first analyzed contact states of roller-raceways and roller-flange under the defective condition. A defected TRBs’ model was then established to obtain the contact load and corresponding contact pressure distribution between each roller and raceway, on the basis of which the friction torque of defected TRBs was evaluated. The results show that defects in the raceway edge induce a large contact pressure peak and uneven contact pressure distribution between roller and raceways. The defects presented on the outer raceway will cause a decrease in the friction torque of TRBs, and the decrement of friction torque is related to the external load and rotating speed of TRBs.