The effects of enzymatic treatments on the properties of coir fiber-reinforced poly(lactic acid) (PLA) were not found in the literature. Accordingly, the effects of various enzymatic treatments on the mechanical performance of the coir fiber-reinforced PLA composites were investigated in the current study. Four different enzymes, namely lipase, lactase, pectinase, and cellulase, were used. The mechanical properties of the composites were determined by the tensile, flexural, impact tests, and dynamic mechanical analysis. According to the test results, the use of enzyme treated coir fibers affected the mechanical properties except for the flexural properties with different extents depending upon their type. The tensile strength increased with the treatments of lipase and lactase, while the treatments with pectinase and cellulase had no remarkable effect. The impact strength was improved with enzymatic treatments except for pectinase. All enzymatic treatments improved the elastic modulus below the glass transition temperature. In brief, enzymatic treatments improved the interfacial adhesion between coir fiber and PLA via the waxes and fatty acids removal and/or the increment in surface roughness.