This study investigated the effect of kenaf parts (kenaf whole stem, kenaf core, and kenaf bast) on the mechanical and physical properties of single-layer and three-layer particleboards made from kenaf (Hibiscus cannabinus L.) and rubberwood (Hevea brasiliensis). The findings showed that the use of kenaf whole stem, which consists of both core and bast, had a positive effect on the modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), permeability, thickness swelling (TS), and water absorption (WA) values of single-layer and three-layer panels. Single-layer admixture panels made from a combination of 70% rubberwood and 30% kenaf had greater strength and stability than single-layer homogeneous panels. The presence of rubberwood particles on surface layers significantly improved the elastic properties of three-layer panels. Panels with kenaf whole stem in the middle layer had better performance than panels with kenaf core. The MOE values of 35RW-30KWS-35RW panels were 56% and 79%, which were higher than those comprising single layers of 100% KWS and 100% KC, respectively. This study suggests that kenaf whole stem is the preferred material to be used in particleboard manufacture incorporated with rubberwood as an admixture for three-layer panels.