In this study, nanocellulose whiskers (NCW) from oil palm empty fruit bunches (OPEFB) were used as reinforcement phase in polylactid acid (PLA). Two techniques were employed to isolate the NCW from OPEFB microcrystalline cellulose (OPEFB-MCC); chemical swelling with DMAc containing 0.5% LiCl to generate the NCW and acid hydrolysis with 64% H2SO4 to generate the NCW-S. The atomic force microscopy showed that the isolated NCW and NCW-S are in nanoscale dimension and displayed an individual rod-like structure. The fillers were then incorporated in PLA matrix at different loadings (1, 3, and 5 parts per hundred resin (phr)) to produce P-NCW and P-NCW-S nanocomposites via solution casting technique. The mechanical properties of the developed nanocomposites were investigated by means of tensile test. The results showed that the tensile strength of nanocomposites increased by 84% and 64% for the NCW and NCW-S reinforced PLA nanocomposites, respectively. The Young's modulus of nanocomposites increased linearly with the fillers loading. Expectedly, the percent elongation at break was impacted negatively as it decreased with fillers loading. The thermogravimetric analysis showed that the decomposition temperatures (T10, T50 and Tmax) of P-NCW were higher than neat PLA. In the case of P-NCW-S however, the thermal stability decreased with the additional of NCW-S.