The Graphostromataceae (Xylariales) mainly contains species known for their endophytic lifestyle, although some may shift to opportunistic pathogenicity under host stress and subsequently colonize woody tissues as saprotrophs. The largest genus, Biscogniauxia, remains largely unexplored and would greatly benefit from a polyphasic taxonomic revision. Likewise, the secondary metabolism of these fungi has been only partially studied compared to related families within the Xylariales, despite their ecological versatility and potential latent pathogenicity. Herein, we introduce Biscogniauxia papillata as a new species from Thailand, based on morphological features and robust multi-locus phylogenetic analyses. Secondary metabolite profiling in different media, followed by preparative chromatography, led to the isolation of a cyclic pentapeptide named cyclobiscognioxin A (1), along with a mellein derivative among its main components. Preliminary biological testing revealed that 1 exhibits potent cytotoxic properties but lacks antimicrobial properties in our assays. The combined morphological and molecular phylogenetic evidence unequivocally distinguishes B. papillata from other members of the genus, confirming its status as a new species. Moreover, our chemical investigation highlights the underexplored biosynthetic potential of Biscogniauxia and expands the known chemical diversity within the genus, which might contribute to their opportunistic lifestyle.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11557-025-02114-y.