The incorporation of small amounts of pyrethroid-based preservatives (Organic solvent-based permethrin (OSP), Water-based permethrin (WP) and deltamethrin) into particleboards made from latex timber clone rubberwood (RRIM 2002) (Hevea brasiliensis ), empty fruit bunches (EFB) of oil palm (Eleasis guineensis ) and rubberwood + EFB (70:30 parts) blend through spraying during blending of furnish significantly increased the resistance of the boards to white rot (Pycnoporous sanguineus ) and subterranean termite (Coptotermes curvignathus ) attacks. This paper discusses the physical and mechanical properties of the pyrethroid-treated particleboards. These properties were compared with those of boric acid-treated and untreated particleboards. The preservative treatment did not significantly affect the internal bond (IB) and modulus of rupture (MOR) of rubberwood and rubberwood + EFB blend particleboards. However, the modulus of elasticity (MOE) of these boards increased when treated with either WP, or OSP. For the EFB boards, all pyrethroid compounds reduced the IB of the board whereas the MOR and MOE were either reduced or unaffected. However, the thickness swelling (TS) of rubberwood particleboard, improved when treated with all the pyrethroid-based preservatives, whilst the other two types of boards were less stable when treated with OSP or WP. Among the three types of particleboards, the mechanical properties of EFB particleboards were affected most by the pyrethroid treatments. The mechanical and physical properties of treated particleboards from rubberwood and admixture were comparable or better than those of the untreated particleboards. Boric acid treatment reduced the MOR of all particleboards but other properties were either improved or unaffected.