Cellulose acetate (CA) is known for its low adsorption affinity toward dyes, hence this study aims to improve its adsorption affinity toward cationic dyes by introducing Cloisite 30B grafted with polyacrylic acid (C30B‐g‐PAA). C30B‐g‐PAA was synthesized by grafting polyacrylic acid (PAA) onto Cloisite 30B (C30B) using in‐situ reversible addition fragmentation chain transfer (RAFT) polymerization. Different weight ratios of unmodified (raw) and modified (C30B‐g‐PAA) C30B (0, 25, and 50 wt%) were incorporated into CA matrices to prepare a series of CA nanocomposite films. The results showed that the adsorption affinity of the prepared nanocomposite films increased toward cationic methylene blue (MB) dye with incorporating either unmodified or modified C30B, but a significant improvement was observed with the incorporating C30B‐g‐PAA with a maximum adsorption capacity of 53 mg/g for a load of 50 wt%. This indicates that the surface modification of C30B with PAA was effective in enhancing the adsorption efficacy of CA. The kinetic and isotherm studies showed that the adsorption behavior of CA nanocomposite film with 50 wt% of C30B‐g‐PAA followed pseudo‐second‐order and Langmuir isothermal model. Regeneration study showed good reusability of CA nanocomposite film with 50 wt% of C30B‐g‐PAA. These results demonstrate that the nanocomposite film with 50 wt% of C30B‐g‐PAA can be used as a highly efficient, easy to separate, and reusable adsorbent material to remove MB dye from wastewater.