Endophytic fungi are a diverse group of microorganisms that colonize the inter- or intracellular spaces of plants for mutual benefits. The interactions with a host plant and other microbiomes are multidimensional and play a crucial role in the production of secondary metabolites. We screened bioactive compounds present in the extracts of Aspergillus flavus, an endophytic fungus isolated from the roots of the medicinal grass Cynodon dactylon, for its anticancer potential. Ethyl acetate extract from isolated A. flavus showed significant cytostatic effects (IC50: 16.25 μg mL−1) against breast cancer cells (MCF-7). Morphology of cells and DAPI stained nuclei along with the results of flow cytometry annexin V/PI assay suggested apoptosis to be the main process leading to cells’ death. While investigating the mechanism that triggers apoptosis, we found that the extract of A. flavus increased ROS generation and caused loss of mitochondrial membrane potential of MCF-7 cells. To identify the metabolites that might be responsible for the anticancer effect, the extract was examined using gas chromatography-mass spectrometry (GC-MS). Interestingly, nine phytochemicals were found to have potential inhibitory effects of anti-apoptotic protein (Bcl-2) in the breast cancer cells. In the in silico molecular docking and molecular dynamics simulation studies revealed that two compounds: 2,4,7-Trinitrofluorenone and 3alpha, 5alpha-Cyclo-ergosta-7,9(11),22t-triene-6beta-ol exhibited significant binding affinities (-9.20, and -9.50 Kcal mol-1, respectively) against Bcl-2 along with binding stability and intermolecular interactions of its ligand-Bcl-2 complexes. Overall, the study found that the endophytic A. flavus from C. dactylon contains plant-like bioactive compounds that have a promising effect in breast cancer.