Abstract: Background and Objective: Guava black spot (GBS) disease is a quiescent infection, that infect immature fruit prior to harvest. Visible symptoms of the disease on guava fruit showed sunken lesions with concentric development, variation in color ranging from greenish black to black and spread in severity affected fruit. An unrecorded disease of guava fruit (Psidiumguajava L.) cv. White Balady, was observed in this study during postharvest disease survey in Egypt. Materials and Methods: Tissues of guava fruit spot used to isolate the pathogenic fungal. To perform the phylogenetic analysis, the internal transcribed spacer (ITS) region amplified by Polymerase chain reaction (PCR). To amplify the ITS, the primer ITS-1 and reverse primer ITS-4 used to amplify rDNA-ITS regions of the fungus. The fungal identification was done by molecular analysis as Phyllostictacapitalensis novel isolate ARAFAT-GF5 according to the GenBank (Accession number–LC269950.1; GI: 119461242) with the synonym: Guignardiamangiferae. Results: The isolate ARAFAT-GF5 (626 bootstrap) used and the Basic Local Alignment Search Tool (BLAST) program used to search for nucleotide sequence homology in GenBank. The computational analysis of the synonymous DNA sequence was useful for predicting the codon profiling. Pathogenicity test performed to complete Koch’s postulates. Typical black spot symptoms developed and the pathogen recovered from the inoculated fruit after 10 days and found as P. capitalensis. Conclusion: This is the first report of black spot disease on guava fruits in Egypt, caused by a novel isolate of P. capitalensis. The results presented here may enable enhancements in the program of integrated disease management.