ABSTRACT Chitin and its oligosaccharides are involved in the plant defense response against fungal pathogens. In most studies, these molecules come from crustacean shell, and there are scarce studies on the use of fungal chitin. Usually the extraction of chitin is by alkaline treatments, which affect the acetylation degree (DA), and the obtaining of oligosaccharides of low molecular weight; so the use of enzymes is proposed as an alternative treatment to obtain chitin oligosaccharides from fungi. The objective of this work was to characterize the chitin fragments of Alternaria alternata extracted by alkaline and enzymatic treatments. The chitin extracted was ultrasonicated and ultrafiltrated to produce chitin fragments. Enzymatic treatments decreased the protein content to 29%, and the bands corresponding to β‐glucans decreased when β‐1,3‐glucanase was applied. Fragments smaller than 1 kDa, DA of 76.7%, and 35.4 μg glucosamine/mg dry weight were obtained by enzymatic treatments. The enzymatic treatments show promising results to extract chitin fragments from A. alternata without severely affect the DA of the molecule. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47339.