<p>In this study, polylactic acid (PLA)/polyethylene oxide (PEO)/cellulose nanocrystal (CNC) nanocomposites were investigated using rheological and thermal analyses to quantitatively evaluate the effects of fabrication methods on CNC dispersion. The nanocomposites were fabricated via two approaches: one-step melt compounding and two-step mixing involving solution dispersion followed by melt compounding. Morphological analysis did not reveal clear differences between the two methods. However, both linear and nonlinear rheological properties sensitively captured differences in CNC dispersion. Nanocomposites prepared by one-step mixing showed negligible changes in rheological behavior upon CNC addition, whereas those prepared by two-step mixing exhibited enhanced rheological responses with increasing CNC content. This improvement was attributed to PEO-mediated dispersion of CNCs, resulting from effective wetting during the solution mixing step. The improved dispersion also influenced thermal properties. While the overall thermal behavior was dominated by the plasticizing effect of PEO, two-step-mixed nanocomposites showed gradual improvements in thermal stability and crystallization behavior with increasing CNC concentration. In contrast, poor CNC dispersion in the one-step-mixed nanocomposites led to deteriorated thermal properties. These results demonstrate that CNC dispersion can be effectively controlled through fabrication methods, enabling tunable rheological and thermal properties in PLA-based nanocomposites.</p>