Egusi melon (Citrullus lanatus) is cultivated in Sub-Saharan Africa mainly for its edible seeds and oil. Its productivity is hindered by leaf blight disease (LBD) in Nigeria. Management of LBD with synthetic fungicides has negative consequences on humans and the environment, necessitating the need to explore biopesticides. This study investigated the antifungal potential of four microbial biocontrol agents (MiBAs) [Trichoderma harzianum(Th), T. pseudokoningii, Bacillus subtilis(Bs), and Pseudomonas fluorescens(Pf)] against Colletotrichum truncatum(Ct), Colletotrichum gloeosporioides(Cg) and Lasiodiplodia theobromae(Lt) causing LBD of Egusi melon in vitro,using dual culture procedure and as seed treatment (1 g mycelial mat of Trichodermaspecies and 1 ml of Pfand Bsat 108cfu/ml/50 seeds) under greenhouse conditions. Mycelial growth, zone of inhibition, disease incidence, severity, number of vines, number of leaves, and vine length were evaluated. Although all MiBAs showed antifungal properties, Trichodermaspecies were more effective than their bacterial counterparts in reducing mycelial growth. Antifungal substances (biotoxins) from the MiBAs were thermostable except on Lt. All MiBAs used as seed treatment significantly reduced disease incidence similarly to fungicide mancozeb, except Pfon Ltinfected plants. MiBAs increased seed germination of Cgand Ltinfected plants, while Thenhanced the plant growth. The antifungal potential of the four bioagents against LBD of Egusi melon was proven while Th(at 1 g/50 seeds) was the most effective, producing the highest pathogen inhibition and plant growth.