Endophytic fungi develop symbiotic connections with their hosts in which they live within plant tissues without causing harm Between 2019 and 2020, thirty samples of Quercus infectoria were collected from various locations in the Duhok province, Kurdistan Regional Government (KRG), Iraq to investigate the presence of endophytic fungus. Different parts of the oak tree (Quercus infectoria), such as the leaf, bud, seed, cork, and lateral branches, were used to isolate the fungal endophytes. Endophytic fungi form symbiotic relationships with their hosts, living within plant tissues without causing harm. A type of xylariaceous fungus called Biscogniauxia mediterranea (B. mediterranea) was isolated from Quercus infectoria (Q. infectoria) in the Duhok area. Molecular and morphological methods were used for identification. Our study represents the first report of B.mediterranea in Iraq and the first isolation as an endophyte from the Q.infectoria plant in the region. Phylogenetic analysis demonstrated the genetic relationship of the Iraqi isolates with strains from different geographic locations. Macrogen Business, a South Korean corporation, conducted bidirectional sequencing on the polymerase chain reaction test (PCR) data. Using BioEdit software, the acquired sequences were edited and assembled, and a consensus sequence was generated for each sample. The sequences underwent Basic Local Alignment Search Tool (BLAST) analysis for the identification of endophytic fungus. The homology of the sequences with reported sequences from other countries ranged from 97.55% to 99.89% as per the National Center for Biotechnology Information's (NCBI) record.