The present work involves the study of the effect of precipitates on mechanical and tribological properties of AZ91 magnesium alloy. Optical microscopy, scanning electron microscopy (SEM), and nanoindentation were used to characterize the microstructures and mechanical properties of the alloy. In addition, the wear behavior of the alloy was deduced using a pin-on disk tribological configuration under unidirectional sliding against steel (AISI 250). The elastic modulus of AZ91 alloy was found to vary significantly with changing precipitation state. The tribological evaluations showed that the specific wear-rate of solutionized sample is lowest as compared to the aged samples. This was attributed to the absence of γ-Mg17Al12 phase. Examination of worn surfaces suggested that microploughing coupled with the adhesive mode of wear is the main wear mechanism in the aged samples.