Rhizophora spp. particleboards with a target density of 1.0 g cm–3 were fabricated from Rhizophora spp. wood particles using formaldehyde resins as binders. Two types of resins, urea-formaldehyde (UF) and phenol-formaldehyde (PF), were used at two treatment levels, 10% and 13%, based on the oven dry weight of the wood particles. The fabricated Rhizophora spp. particleboard samples with 13% PF and 13% UF had densities nearest to the density of water at 0.978 g cm–3 and 0.914 g cm–3, respectively. By contrast, the densities of the Rhizophora spp. particleboards at the 10% PF and 10% UF treatment levels were 0.894 g cm–3 and 0.885 g cm–3, respectively. The mass attenuation coefficients of the fabricated Rhizophora spp. particleboards were determined using X-ray fluorescence (XRF) beams generated from high-purity zirconium, molybdenum, tin and palladium metal plates. The excitation source used was an annular Am-241 source with an activity of 3.7 GBq. The Kα energy of the XRF emitted from these metal plates ranged from 15.77 keV to 25.27 keV. The mass attenuation coefficient of 10% PF Rhizophora spp. particleboard was the closest to the mass attenuation coefficient of water at these photon energies.