Abstract This study concentrates on a laboratory assessment to evaluate the efficiency of adding cellulose fibre isolated from an oil palm bark in lightweight foamcrete (LF) to improve the strength properties. LF samples were strengthened with 0.1%, 0.2%, 0.3%, and 0.4% volume fractions of cellulose frond fibre (CFF). There were three low densities of LF were considered, namely 500 kg/m³, 750 kg/m³, and 1000 kg/m³. The parameters investigated were compressive, splitting tensile and bending strengths. The results indicated that the presence of 0.3% CFF in LF helped to obtain the highest results for bending, compressive and splitting tensile strengths. CFF acts as a space filler and bridges the gaps and microcracks in LF, resulting in high strength. In addition, CFF helped to inhibit the micro-cracks propagation in the plastic state of LF. This study provided vital experimental data to assist future researchers in the field of LF in utilizing natural fibers to enhance the properties of LF.