Biodegradable polylactic acid (PLA) nanocomposite films with organically modified nanoclay (PKL_DS) and silica from rice husk ash (SiRHA) incorporation were prepared using a solvent casting method. The morphology and water vapor transmission rate behavior of these PLA based nanocomposite films with the addition of PKL_DS and SiRHA fillers was investigated at various loadings. The morphology of the nanocomposite was examined using X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was confirmed that PLA molecular chains were intercalated into the interlayers of nanoclay (PKL_DS), which was well dispersed in the PLA matrix. TEM results showed SiRHA agglomerates and poor dispersion. The scanning electron microscopy (SEM) results showed good dispersion and good compatibility between nanoclay (PKL_DS) and the PLA matrix, while the SiRHA filler exhibited phase separation, silica agglomeration and some pore structures in the PLA matrix. The surface of the nanocomposite film with the incorporation of a SiRHA/PKL_DS combination exhibited a dense structure. A maximum reduction of 67% of water vapor transmission rate (WVTR) was obtained for nanocomposite films with co-addition of 10 wt% PKL_DS and 3 wt% SiRHA over that of PLA alone. It is concluded that the incorporation of a SiRHA/PKL_DS combination was very effective in improving the water vapor barrier property of a PLA based nanocomposite.