The interfacial reaction behavior of Al and Ti₃AlC₂ at different pouring temperatures and its effect on the microstructure and mechanical properties of the composites were investigated. The results show that the addition of 3.0 wt.% Ti₃AlC₂ refines the average grain size of α(Al) in the composite by 50.1% compared to Al6061 alloy. Morphological analyses indicate that an in-situ Al₃Ti transition layer of ~180 nm in thickness is generated around the edge of Ti₃AlC₂ at 720 °C, forming a well-bonded Al-Al₃Ti interface. At this processing temperature, the ultimate tensile strength of Al6061-3.0 wt.%Ti₃AlC₂ composite is 199.2 MPa, an improvement of 41.5% over the Al6061 matrix. Mechanism analyses further elucidate that 720 °C is favourable for forming the nano-sized transition layer at the Ti₃AlC₂ edges. And, the thermal mismatch strengthening plays a dominant role in this state, with a strengthening contribution of about 74.8%.