Arecanut leaf sheath (ANLS) an unexplored agricultural biomass is used to recover long staple lignocellulosic fibers. A long staple lignocellulosic fiber is extracted from ANLS biomass using 8% NaOH treatment. As reinforcing material ANLS fibre properties such as fibre length, diameter, moisture content, single fibre strength and X-ray diffraction analysis were carried out. Three types of composites, 15, 20 and 25 (w/w)% fibre loading composites have been prepared in unsaturated polyester resin matrix. The tensile, flexural and interlaminar shear strength (ILSS) properties and void content of these composites are studied. The tensile fracture behaviors of fibre and composites are studied with the help of scanning electron micrographs. © 2021 The Textile Institute.