Nowadays, Chitosan has attained more attention due to its potential applications in food, agriculture and pharmaceutics. The cationic nature of chitosan enhances the film forming capacity of this polymer. However, films made only from chitosan lack water resistance and have reduced mechanical properties. The functional properties of chitosan films can be improved when chitosan films are combined with other film forming materials. The objective of this study was to prepare chitosan based antimicrobial films by the incorporation of streptomycin loaded starch Nanocrystals. Different properties of this film such as swelling nature, moisture content, degradation nature and the antimicrobial activity of modified chitosan films were investigated. Drug releasing efficacy of the film was also studied. The addition of streptomycin loaded Starch nanocrystals in chitosan-gelatin film increased crystallinity of the film, lowered the swelling nature of the film to a controlled manner. Moreover the Modified chitosan based antimicrobial film showed almost 90% of Escherichia coli inhibition and 80% of Bacillus subtilis inhibition and also the film showed a sustained release (60%) of streptomycin for 10 days.