Abstract Dissimilar AA5083 and C101 pure copper linear friction welds were prepared using different forging pressures (60 MPa, 80 MPa, and 110 MPa) to investigate the influence of the forging pressure on the microstructural and mechanical properties development using optical microscopy (OM), scanning electron microscopy (SEM), hardness measurements, and tensile testing. The in-situ generated intermetallic particles in the vicinity of the weld line were characterised using electron probe micro-analyser (EPMA), to rationalise their impact on the mechanical properties. The results showed that the process led to the formation of various intermetallic phases as well as the entrainment of base material fragments in the vicinity of the weld interface. In general, high forging pressure corresponding to high welding heat input resulted in the formation of a layered intermetallic phase (identified as Al2CuMg), which was the most detrimental to the mechanical properties, compared with a scattered distribution of fragmented Cu and intermetallic particles across the joint interface.