Introduction. Concerns about the potentiallyharmful effects of fungicides on human health and the environmentencourage the search for alternative treatments for perishable fruitpostharvest disease control. To this end, the potential use of oligochitosan asa natural antifungal compound to control postharvest anthracnosecaused by Colletotrichum musae was investigatedin banana fruits from the Cavendish group (genome AAA). Materials andmethods. The influence of oligochitosan on the growth of C. musae was determined in vitro bymicrographic analysis, while its in situ antifungalactivity was monitored in banana fruits that were artificially injury-inoculatedwith C. musae; the activities of several defense-relatedenzymes were measured. Results and discussion.Oligochitosan at (4 and 8) g·L–1 markedly inhibited radialmycelial growth of C. musae in vitro. The scanningelectron micrograph of C. musae treated with oligochitosanat inhibitory concentrations showed distortion and thinning of thehyphal wall and reduction in fungus colony diameter. Dipping banana fruitsin oligochitosan solution at (5 to 20) g·L–1 significantly reducedthe diameter of the anthracnose lesion, and 20 g oligochitosan·L–1 almostreached the same inhibitory effect as 0.5 g·L–1 of Sportak®, a synthetic fungicide. Activities of defense-relatedenzymes such as phenylalanine ammonia-lyase (PAL), β-1, 3-glucanase(GLU) and chitinase (CHT), but not polyphenol oxidase (PPO), increasedin banana fruits treated with 0.5 g oligochitosan·L–1. Conclusion. The inhibitory effect of oligochitosanon anthracnose development is due to the combination of a directantifungal effect on the pathogen and an indirect effect, wherebythe activities of defense-related enzymes in the banana fruit were enhanced.To control anthracnose in harvested bananas, treatment with oligochitosanabove 20 g·L–1 may substitute the use of synthetic fungicide.