The effects of heat treatments on microstructure and basic mechanical properties of selective laser melted (SLM) TC4 titanium alloy were investigated in detail. The results demonstrated that a lot of acicular α/α′ and β phases exist in the SLM TC4 titanium alloy. With the increase in the aging treatment temperature, the metastable α′ phase of SLM TC4 was decomposed into α + β laths. Moreover, the α/α′ phase and β phase grew coarser, leading to a gradual decrease in strength, that is, plasticity and hardness increased and decreased, respectively. In terms of solid-solution aging treatment, the β phase was transformed into the α′ martensite phase in the solid-solution treatment, and the aging treatment induced the decomposition of the metastable α′ phase into α + β laths. The strength and hardness of SLM TC4 alloy increased as the temperature increased. The optimal mechanical properties could be obtained by water quenching after holding at 960 ℃ for 1 h and then air cooling after holding at 600 °C for 8 h.