This study investigates the effect of forging pressure on the microstructural evolution, mechanical properties, and fracture behaviour of rotary friction welded (RFW) low-alloy steel (LAS) joints. Three forging pressures – 0.76, 0.84, and 0.91 MPa/s – were applied to evaluate their influence on hardness, tensile strength, and ductility. Microstructural analysis revealed that at 0.84 MPa/s, significant grain refinement occurred in the heat-affected zone, promoting superior mechanical properties. The ultimate tensile strength increased from 473 MPa at 0.76 MPa/s to 488 MPa at 0.84 MPa/s, before slightly decreasing to 482 MPa at 0.91 MPa/s due to grain coarsening. A maximum elongation of 40.01% was achieved at 0.84 MPa/s, representing a 27.05% improvement compared to 0.76 MPa/s. Hardness variations followed a similar trend, with peak values observed at intermediate forging pressure. Fractographic analysis confirmed a ductile fracture mode at 0.84 MPa/s, characterised by deep equiaxed dimples, while coarser fracture features were noted at higher pressures. These results demonstrate that an optimal forging pressure enhances strength-ductility synergy by refining the microstructure and preventing excessive grain growth. The findings provide valuable insights into optimising forging conditions for high-performance RFW LAS joints in structural and industrial applications.