The elastic moduli of PLA reinforced with 5 and 10 wt.% CNF with the carrier, at a frequency (ω) of0.07, were 67% and 415% higher, respectively, than that of neat PLA. The shear viscosity at a shear rateof 0.01 (0.01) for PLA + 10 wt.% CNF was 32% higher than that of the neat PLA matrix. The 0.01of PLAreinforced with 5 wt.% CNF and the PHB carrier was similar to neat PLA. The tensile and flexural moduliof elasticity of the nanocomposites continuously increased with increased CNF loading. The results of themechanical property measurements are in accordance with the rheological data. The CNF appeared to bebetter dispersed (less-aggregated nanofibers) in the PLA reinforced with 5 wt.% CNF and the PHB carrier.Possible applications for the composites studied in this research are packaging materials, constructionmaterials, and auto parts for interior applications.