The antagonistic activity of Aspergillus piperis against Fusarium oxysporum f. sp. fabae (FOF) and Sclerotinia sclerotiorum were examined and showed multiple signs of hyphal interactions. Microscopic examination of contact regions among A. piperis and each pathogen revealed distinct enzymatic lysis of pathogenic hyphal cell walls. Therefore, it is important to estimate the lytic enzyme activity of A. piperis. Extracellular lytic enzymes are important offensive forces for A. piperis as a biological control agent. Chitinase, phospholipase, and protease recorded relatively high activity from a culture age of 10 days (82.3, 42.4, and 6.2 U/ml, respectively). Enzymatic persistence was measured at room temperature, recording relatively long periods, saving 54%, 46%, and 21% of their activity, respectively. The cytotoxicity of the crude culture filtrate of A. piperis was examined in MCF7 and WI38 human cell lines. The cell viability (IC₅₀) value of the fungal filtrate was estimated after 24 h and 48 h. The results revealed that IC₅₀ values against the MCF7 cell line were inoperative after 24 h and were recorded 80 μg/ml after 48 h. In contrast, IC₅₀ values against the WI38 cell line were 85.69 and 69.8 μg/ml after 24 and 48 h, respectively.