In this study, three different coatings, viz., Sr–P chemical conversion coating, electroless Ni–P/Sr–P bilayer coating, and electroless Ni–P–Al2O3/Sr–P coating with composite top layer, were deposited on aerospace-grade AZ91D Mg alloy for the purpose of enhancing the wear resistance of the latter. Surface morphology of the coatings was studied through scanning electron microscopy while the chemical composition was studied with energy dispersive spectroscopy (EDS). Structural investigation was conducted through grazing incidence X-ray diffraction (GIXRD). Adhesion behaviour of the coatings was assessed through scratch test. Tribological characteristics of the samples were studied through pin-on-disc test with HcHCr steel ball counterbody under 10 N normal load in unlubricated condition. Surface morphological and EDS spectra suggested the appearance of Sr–P layer in the form of dispersed flakes. The Ni–P layer, however, uniformly enveloped the bottom Sr–P layer. Al2O3 nanoparticles were found to be uniformly distributed and embedded in the Ni–P matrix for the composite coating. The presence of Al2O3 as separate entity in the Ni–P matrix was also confirmed through GIXRD spectra wherein characteristic peaks of Al2O3 were registered. Critical load of adhesion (Lc3) was highest at 30 N for the Ni–P–Al2O3/Sr–P composite layer among the other two coatings. Superior scratch resistance for the same was also revealed from the minimum damage due to scratching. In pin-on-disc test, the uncoated alloy displayed coefficient of friction of ~ 0.7, which significantly reduced for the Ni–P–Al2O3/Sr–P composite layer to ~ 0.25. Marked reduction in width of the wear track with fewer sliding marks for the composite coating as compared to other samples indicated excellent wear resistance of the same which was also corroborated through the estimation of wear coefficients.