AbstractThe demand of natural fiber reinforced composites has grown enormously in polymer industries owing to their renewability and sustainability and maintaining their performance and properties. In this investigation, two natural fibers have been considered as a reinforcer to develop chemically functionalized high‐density polyethylene (CF‐HDPE)‐based composites. The total holocellulose content of ~85% and ~65% for nettle fiber (NTF) and oil palm empty fruit bunch fiber (OPF) make them significant for this study. OPF/CF‐HDPE and NTF/CF‐HDPE composites have been developed and characterized to measure their desirable properties. The structural confirmation suggests reinforcement/matrix adhesion through ester and hydrogen bonds between them. NTF/CF‐HDPE and OPF/CF‐HDPE are thermally stable upto 240°C and 250°C, respectively. A significant increment of ~40% and ~64% in tensile strength were observed in addition of OPF and NTF reinforcer in pristine matrix. A similar observation has been shown in flexural strength with improvement of ~58% and ~83% with OPF and NTF as reinforcer. Among all these composite compositions, the 30/70 NTF/CF‐HDPE composite demonstrated the highest tensile and flexural properties values due to higher holocellulose of NTF. This study demonstrates the potential of OPF and NTF reinforcer to develop natural fiber reinforced polymer composites, which helps respective industries to manufactured tailored made products with desirable properties.Highlights OPF/CF‐HDPE and NTF/CF‐HDPE composites are sustainable and low cost. The composite compositions have been developed by extrusion and injection molding. The composite's mechanical (tensile and flexural) properties have been demonstrated. SEM and FTIR characterized the composites for the fiber/matrix adhesion. The composite's thermal stability has been affected by fibers and matrix.