Natural fiber composites have industrially attractive because of their low density, low cost, and comparable specific mechanical properties with synthetic fiber. The extrusion and injection molding method is used to fabricate the sisal fiber-reinforced PLA biodegradable composites with random fiber orientations. The fiber weight fraction varied from 0 to 30 wt. % (in the step of 10 %), and the influence of the fiber weight fraction of biocomposite on different properties was studied. The composites are tested for evaluating the physical properties, viz. density, hardness, and water absorption and vibration characteristics, viz. natural frequency and damping ratio. The density of Sisal/PLA biocomposites was seen from 1.18 to 1.23 gm/cm3 and hardness from 93.84 to 97.28. In water absorption, as the weight percentage of sisal increases, the diffusion and permeability coefficient increase and reach 2.83E-05 and 8.11E-06, respectively, for 30 % sisal loading. The fundamental natural frequencies and damping ratio of 30 wt. % sisal fiber biocomposite are 24.41 Hz and 0.1450, respectively, higher than the pure PLA. This is observed for all vibration modes, and the reason behind this is the high stiffness of fibers. These developed biodegradable composites help lower the cost of purePLA-based composites and have wise applications in packaging and allied industries.