A series of TiAlCrMn high entropy alloys (HEAs) with variable atomic ratios of Al, Cr, and Mn were prepared using vacuum melting. High-temperature oxidation behaviors and mechanical properties were investigated before and after heat treatment. The oxidation mass gain rate is declined dramatically with increasing Al, Cr, and Mn element contents. Enhanced oxidation resistance is attributed to a continuously dense (Al,Cr)-rich oxidation layer, which can hinder the inter-diffusion of O and alloying elements. Furthermore, microhardness increases monotonously with increasing Al, Cr, and Mn element contents of the alloys before and after heat treatment. Grain coarsening can result in lower microhardness, but precipitation strengthening contributes to higher hardness of the alloys with high alloying element contents. Meanwhile, deformation-induced strengthening also contributes to higher compressive strength. The value after heat treatment at 500 °C is lower than that of as-cast samples while an increased value occurs after heat treatment at 900 °C accompanied by sacrificing the malleability.