Surface treatment of natural fibers is one of the important methods to improve the mechanical properties of the composite material. In this paper, plasma treatment (PT) for various exposure timings (30, 60, 90, and 120 s) was performed to study the mechanical properties of jute fiber and its composites using poly (lactic acid) (PLA) as the matrix. The results were compared with alkali (AT) and plasma treated (PT) fiber composites. Bundle fiber test was carried out for untreated, AT, and PT jute fiber composites. PT fiber composites showed superior properties compared to other treatments. Micro-droplet test results showed that the interfacial shear strength (IFSS) of PT fiber composite is higher than that of AT fiber composites. Mechanical properties and hardness were increased on subjecting the fiber to plasma treatment. Tensile strength, young’s modulus and flexural strength were increased in an order of 28, 17, and 20%, respectively, for plasma polymerized jute fiber composites. Moreover, plasma polymerization leads to increase (>20%) in the flexural strength than untreated fiber composites. It is inferred that plasma treatment improves the interfacial adhesion between the jute fiber and PLA. These results were also confirmed by scanning electron microscopy observations of the fractured surfaces of the composites. Overall, plasma polymerization is an effective and eco-friendly method for the surface modification of the lingo cellulosic fiber to increase the compatibility between the matrix (hydrophobic) and fiber (hydrophilic).