Studies had been carried out to look for new phantom materials in medical physics that can provide better dose accuracy in comparison to water. This study focused on the fabrication and characterisations and of particleboards made of Rhizophora spp. as phantom for low and diagnostic photon energies. Rhizophora spp. particleboards were fabricated at different particle size ranges of 104–210 μm, 74–104 μm and ≤ 74 μm. Corn starch was used as adhesive at 5% and 10% percentage levels as well as the binderless particleboards. All particleboards were fabricated with density similar to water at 1.0 g cm–3. The physical and mechanical properties of the particleboards were evaluated based on the Japanese Industrial Standards (JIS A 5908:2003). The elemental compositions and the effective atomic number of corn starch bonded Rhizophora spp. were determined based on the energy dispersive X-ray analysis (EDXA). The mass attenuation coefficients were measured by using X-ray fluorescence (XRF) photons between 16.59 keV and 25.26 keV. The computed tomography (CT) numbers, electron density and density profiles were investigated by using the CT scanner and compared to water. The Rhizophora spp. particleboard with highest percentage level of corn starch (10%) and smallest particle size (≤74 μm) showed the highest physical and mechanical properties shown by the average internal bond (IB) strength and modulus of rupture (MOR). The calculated effective atomic number of the corn starch bonded Rhizophora spp. particleboard was closer to water compared to the binderless particleboards. All particleboards showed close values of mass attenuation coefficients to water at all experimented photon energies. All Rhizophora spp. particleboards also showed CT number close to water within 5.4% percentage of difference. The results showed that the addition of corn starch improved the physical properties of Rhizophora spp. particleboards and can be potentially used as phantom material for low and diagnostic photon energies.