Despite their better mechanical qualities, plant fibers are now appreciated enough to be employed as an additional component in composite manufacture rather than synthetic materials. Industries are making efforts to preserve nature's ecological equilibrium in order to avoid catastrophic natural disasters. This study investigated thermal, mechanical, morphological, and moisture‐capture capabilities of Licuala grandis leaf stalk fibers (LGLSFs) reinforced in an unsaturated polyester resin (UPR) matrix biocomposite. Biocomposites were fabricated by compression molding technology, with different weight ratios and sizes. The biocomposite containing 30 wt.% and 5 mm length LGLSF had best mechanical properties, with equal impact (5.4 J/cm2), hardness (70.4 HRRW), flexural (58 MPa), and tensile (64.9 MPa) values. Furthermore, prolonging LGLSF reinforcement to 15 mm increased the bio‐composite specimen's tensile, flexural, hardness, and impact characteristics by 9.09%, 9.65%, 14.8%, and 6.25%, respectively. The Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) spectra were analyzed to determine the bio‐composite's feasibility for commercial use. The bio‐composite specimen is ideal for usage in vehicle and aviation upholstery due to its sufficient hydrophobicity, lowered density, and heat resistance up to 236 °C, which are accomplished through a sufficient weight ratio of LGLSF and UPR, as well as LGLSF dimensions.