Abstract: As-cast Ti₂₈Co₁₄Ni_37.12Zr_20.88 high entropy alloy was tempered at different temperatures ( 673,723 K). The effects of tempering temperature on the microstructure and mechanical properties of the high entropy alloy were studied. The results show that the microstructures of the as-cast, 673 K tempered and 723 K tempered alloy were composed of a TiNi matrix phase of a body-centered cubic structure and a small amount of a face centered cubic structure Ti₂Ni second phase. With the increase of tempering temperature, the grains of TiNi phase and Ti₂Ni phase were refined. After tempering heat treatment, the elastic limit and yield strength of the as-cast alloy increased. The compressive strength of the 673 K tempered alloy was lower than that of the as-cast alloy, but when the tempering temperature increased to 723 K, the compressive strength increased and was higher than that of the as-cast alloy. The fracture mechanism of the as-cast high entropy alloy was mainly cleavage fracture, supplemented by intergranular fracture and ductile fracture. The fracture mechanism of the 673 K tempered and 723 K tempered high entropy alloy was mainly cleavage fracture, supplemented by intergranular fracture.