In this study, based on research conducted between 2023 and 2024 in the Mamora cork oak forest, various symptoms were observed and described in cork oak trees: defoliation and dieback of branch tips, abnormal discoloration of young shoots, twigs, and branches, alterations to the bark and wood, sap flow from branches and trunks, and bark peeling. The dieback was observed on old cork oak stumps and on young trees from reforestation projects. This study aimed to identify and study the fungal complex associated with the cankers visible on the trunks and branches of the cork oak. Samples taken from the cankers underwent two types of complementary analysis: 1) scraping of the canker patches and microscopic observation of the fungal spores present, and 2) incubation of the canker patches using the blotter test and transfer of the resulting spores onto a culture medium. The results revealed the presence of Biscogniauxia mediterranea, a fungus responsible for canker and cork oak dieback, accompanied by a diverse fungal complex including various genera: Bipolaris, Alternaria, Pestalotia, Torula, and Fusarium. These findings, which significantly improve our understanding of the health condition of the Mamora cork oak forest, constitute a preliminary but essential step toward future comprehensive studies aimed at developing effective prevention and protection strategies for cork oaks.