The cocoyam (Xanthosoma sagittifolium) is contains many carbohydrates that can be used as a source of starch modification. Unmodified starch has a long cooking time, low viscosity, solubility and swelling power. Modification of cocoyam flour was done with lactic acid bacteria (Lactobacillus plantarum). This study aimed to explore the capability of local tubers and to determine the physicochemical characteristics of modified cocoyam flour with lactic acid bacteria. This research method using a randomized block design with two factors. Data were analyzed by the analysis of variance method and a further test of DMRT. The concentrations of L. plantarum used were 3%, 5% and 7% and fermentation time of 48, 72 and 96 h. The best result of this research was obtained using 7% L. plantarum bacteria and fermentation time of 96 h yielding physicochemical characteristics of water content 8.28%, ash 1.05%, swelling power 5.78%, solubility 51.93%, starch 76.47%, amylose 26.28% and color 87.42%. Fermentation significantly increased the swelling power, water content and solubility, while starch and amylose decreased.