Rotary friction welding is a promising solid-state joining technique for dissimilar aluminium–copper joints. This study investigated the effects of friction time (30–60 s) and rotational speed (1000–2000 rpm) on the microstructure and mechanical properties of AA6061–Cu joints. The welded joints were characterized by optical microscopy, SEM–EDX, micro-Vickers hardness, and tensile testing. Increasing the friction time from 30 to 60 s increased the ultimate tensile strength from 19.15 MPa to 28.44 MPa and increased the average IMC thickness from 43.68 μm to 136.78 μm. At a constant friction time of 60 s, the rotational speed of 1300 rpm produced the highest tensile strength of 63.90 MPa, the highest average hardness of 74.52 HV, and an average IMC thickness of 204.61 μm. These results indicate that appropriate control of friction time and rotational speed improves interfacial bonding and mechanical performance through controlled IMC evolution and thermo-mechanical interaction. Keywords: Aluminium, Copper, Friction Time, Rotary Friction Welding, Rotational Speed.