The use of agrochemicals has caused environmental problems and toxicity to humans, so natural alternatives for disease control during harvest and postharvest have been evaluated. The aim of this study was to evaluate cinnamon essential oil, neem oil, and black sapote fruit extract for in vitro inhibition of fungi isolated from chayote fruit. The extracts were applied at 300, 350, and 400 ppm in Petri dishes and the mycelial growth ofFusarium oxysporum, Fusarium solani, Goetrichumsp., andPhytophthora capsiciwas evaluated for 7 days, and the percentage of mycelial growth inhibition per day was calculated. Cinnamon oil showed a fungicidal effect at all concentrations. Neem oil at 400 ppm showed a 42.3% reduction in the growth ofF. solaniand 27.8% reduction in the growth ofF. oxysporum,while at 350 ppm it inhibited the mycelial growth ofPhytophthora capsiciby 53.3% and ofGoetrichumsp. by 20.9%; finally, the black sapote extract at 400 ppm inhibited 21.9–28.6% of the growth of all fungi. The growth of postharvest fungi on chayote fruit could be prevented or reduced by applying the plant extracts evaluated at adequate concentrations.