⋅Hye-Jung Cho 2 ⋅Sun-Young Lee 2, † ABSTRACT1 )Cellulose acetate (CA) has been widely utilized for composite materials due to its high transparency and thermal resistance. In this study, CNCs (cellulose nanocrystals) were reinforced in CA nanocomposites for fortifying mechanical properties of the composites. In addition, CA nanocomposites reinforced with CNCs were manufactured by extrusion/ injection processes applied with CNC-predispersion method for achieving a high dispersion level of CNCs in the CA matrix. According to the analysis of mechanical properties, the CA nanocomposite with 3 wt% CNCs has the highest tensile and flexural strengths due to the reinforcing effect of CNC nanoparticles. Thermogravimetric analysis (TGA) showed that the addition of acid hydrolyzed CNCs slightly lowered the initial pyrolysis temperature of CA nanocomposite.