The effect of compatibilization on the reciprocating frictional behavior of a polyamide 66 (PA66)/ultra-high molecular weight polyethylene (UHMWPE) blend was investigated. The influence of the amount of added maleic anhydride–grafted polyethylene (MAH-g-HDPE) on the phase morphology, compatibility, and viscoelasticity was explored using scanning electric microscopy (SEM), dynamic mechanical analysis (DMA), and capillary rheometry. In addition, the effect of MAH-g-HDPE on the reciprocating friction and wear performance of the PA66/UHMWPE blend was tested. The worn surface, transfer film, and wear debris were analyzed using SEM, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The results showed that the maleic anhydride groups in the MAH-g-HDPE improved the compatibility of PA66 and UHMWPE, and the addition of MAH-g-HDPE enhanced the interface bonding strength and lowered the polar difference between PA and UHMWPE. Therefore, the improved compatibility enhanced the wear resistance of the blend. During reciprocating sliding, UHMWPE transferred to the counterface prior to PA66 for the incompatible blend. The addition of MAH-g-HDPE promoted the adhesion and transfer of PA66 to the counterface.