Investigating the swelling properties of chitosan (Cs) film was deemed meaningful, as it plays an important role in predicting the life span of the film. Due to the limits in stability properties, the insertion of reinforcement agent is expected to increase the properties of Cs film. To this purpose, 1,2,4,5-benzenetetracarboxylic-chitosan (BTC) filler was inserted into the Cs matrix. The effect on the degree of swelling (Q (t) ) and the rate of swelling (Q (r) ) of the composite film at varying compositions of BTC filler (0, 2, 4, 6, 8, 10 and 12 wt/v%) was investigated. The Q (r) and Q (t) both decrease with an increasing BTC content, which may be attributed to the looser packaging structure, and the improvement of the hydrophobic character of the composites film. Thus, the addition of BTC filler, up to 10 wt/v%, makes the Cs film more stable with a prolonged swelling time. Meanwhile, electrostatic interaction and hydrogen bonding between the swelling medium and neutral groups, of the polymeric chains of the composites, contributed to the obtained values of Q (t) and Q (r) . The FTIR results support the argument for the Q (t) and Q (r) values of different compositions of BTC filler in the Cs matrix, in the different swelling medium (pH 2-14).