This study aims to investigate the natural cellulosic fibers extracted from novel Ziziphus Mauritiana plants. The fibers were treated with alkali solution and epoxy composites were developed for both untreated and chemically modified fibers through hand lay-up process. Physico-chemical and thermomechanical characterization were carried for both untreated and alkali treated Ziziphus Mauritiana fibers through physical analysis, chemical analysis, Thermogravimetric analysis, Fourier transform infrared spectroscopy, X-Ray diffraction test and single fiber tensile test. The alkali treatment facilitates to remove amorphous constituents and improves the crystalline index by 1.31 times, thermal stability by 1.15 times and fiber strength by 1.44 times, which is supported by chemical analysis and Fourier transform infrared spectroscopy analysis. Later, developed Ziziphus Mauritiana composites were analyzed as per ASTM for its mechanical and sound absorption characteristics. The reduction in amorphous constituents after chemical treatment improved the surface roughness in alkali-treated Ziziphus Mauritiana fibers which influenced the bonding behavior. Also it improved the ultimate tensile strength by 2.12 times, flexural strength by 1.38 times and sound absorption coefficient by 1.15 times. Thus, the Ziziphus Mauritiana fibers are potentially suitable for use in lightweight structures.