After adjusting the MOR and MOE values of the fiber-reinforced particleboards for the effect of density variation, significant differences (p = 0.0158) were observed when 100% Wood particleboard was compared to Wood–Flax and Wood–Hemp. A percent increase in MOR and MOE of 42 and 28% was recorded for the Wood–Flax boards and 53 and 32% for the Wood–Hemp boards. The higher flexure properties observed for particleboards with the fiber-reinforced particleboards is largely due to the tensile strength and modulus contribution of the fibers which have been reported to be in the range of 800–1500 MPa and 60–80 GPa for Flax and 550–900 MPa and 70 GPa for Hemp respectively (Anandjiwala and Blouw, 2007). A comparison between the 100% Hurd particleboard and the Hurd–Hemp fiber-reinforced board yielded significant differences (p < 0.0001), with the Hurd–Hemp boards 60% stronger and 46% stiffer than the 100 (% Hurd boards. Particleboards containing shive material, that is the 100% and Shive–Shive Flax, were only significantly different (p = 0.0005) in terms of their bending stiffness values (27% increase for the Shive–Flax boards) but not their bending strength.