This study investigates the feasibility of utilizing kenaf core and kelempayan as alternative raw materials for the production of low-density particleboard. These rapidly proliferating species were introduced in Malaysia to guarantee a sustained supply of wood composites. This study sought to assess the impact of different board densities and particle ratios on the mechanical and physical properties of particleboard. Panels were manufactured at three densities—300, 400, and 500 kg/m³—utilizing two particle ratios of kenaf core (KC) and kelempayan (K): 30:70 and 50:50. Urea formaldehyde (UF) resin functioned as the adhesive agent. The evaluated mechanical qualities were modulus of elasticity (MOE), modulus of rupture (MOR), and internal bonding (IB), whilst the physical properties assessed included thickness swelling (TS) and water absorption (WA), in line with Japanese Industrial Standard JIS A 5908: 2003. The findings indicated that augmenting both the density and the ratio of kenaf core enhances the mechanical and physical properties of the particleboard. Boards with a density of 500 kg/m³ exhibited superior mechanical strength, with a modulus of elasticity (MOE) of 1127 MPa, a modulus of rupture (MOR) of 7.91 MPa, and an internal bonding (IB) strength of 2.01 MPa. Nonetheless, these denser boards demonstrated subpar performance for water absorption (133%) and thickness swelling (21.94%). Moreover, particleboards with a 50:50 ratio of KC to K surpassed those with a 30:70 ratio in both mechanical and physical properties. Notwithstanding these findings, the particleboards failed to satisfy the minimum criteria established by the standard, with the exception of internal bonding (IB).