The utilisation of wood-processing residues in particleboard production provides an opportunity to improve resource efficiency. However, limited research has systematically examined the combined influence of material characteristics and fabrication parameters on panel performance. This study investigates the joint influence of particle mix, resin content and processing method on the performance of particleboards manufactured from radiata pine (Pinus radiata) wood residues. Single-layer panels were fabricated using coarse particles, thin particles, and a thin–fine particle blend at three resin contents via dry and water-conditioned fabrication methods, targeting a constant density of 600 kg/m³. Panels were evaluated for modulus of rupture (MOR), modulus of elasticity (MOE), thickness swelling (TS) and water absorption (WA). The results revealed statistically significant interaction effects among the factors, with particle geometry primarily governing bending performance, and fabrication route exerting the strongest influence on dimensional stability. Thin-particle panels exhibited the highest bending performance, with the 12 wt.% dry-fabrication method achieving an average MOE of 1862 MPa and MOR of 14.65 MPa. In contrast, fine-particle incorporation reduced bending performance but improved dimensional stability, with micro-CT analysis showing lower porosity and smaller pore features in the selected fines-containing panel, reaching a minimum porosity of 3.6%. Overall, the findings demonstrate that coordinated optimisation of material composition and processing parameters can enhance the performance of residue-based particleboards.