Castanea sativa Mill. is a species belonging to the family Fagaceae, a woody tree that is very common and useful in Mediterranean areas , however, an epidemic from 1990s is causing a tremendous harm in Skikda (Province, Algeria) that was occasionally fatal due to unknown factors. These symptoms led us to carry out an in-depth diagnosis in order to determine the causal agent of this disease, suggesting that fungi could be responsible. For this purpose, isolation was carried out on a PDA (potatoes dextrose agar) medium at 28°C from the soil, roots and leaves of the trees. After macroscopic and microscopic identification of the fungal isolates, pathogenic species used as an inoculum during the growth of seeds determined that ten species belonging to major nine genera of different phylum were isolated and identified. Verticillium sp. was prevailed with 30% in soil, 45% in roots, and 53% in leaves of trees. The identification of the causal agents using inoculation divulged the presence of Verticillium sp. as the highest probable cause of this damage and Fusarium sp. with lower probability.