The current trial aimed to investigate the ameliorative effect of pumpkin seeds extract (PSE, Cucurbita maxima)-supplemented diets against ochratoxin A (OTA) toxicity in terms of growth performance, serum biochemical parameters, antioxidative enzymes, immunity parameters and intestine and liver histopathology of Nile tilapia (Oreochromis niloticus). Two hundred randomly distributed healthy fish (initial weight = 16.84 ± 0.061 g) were divided into four diverse groups. Each group of fish was stocked into five aquaria, each containing 10 fish. The first group was served as control and fed a basal contaminated diet (600 μg OTA/kg diet) while the other three groups were fed OTA contaminated diets and supplemented with graded amounts of PSE (0.25, 0.5 or 1 mg/kg). The treatments used were as follows: OTA + PSE (0.25), OTA + PSE (0.5), and OTA + PSE (1). The results showed that fish administered high levels of PSE significantly boosted growth and feed efficiency parameters. Additionally, supplementing OTA-contaminated diets with 1 mg PSE/kg diet reduced the deleterious effects of OTA on liver enzyme activities (aspartate aminotransferase, and alanine amniotransferase). Meanwhile, the protein constituents were significantly improved in all PSE-supplemented groups. In the same context, the antioxidant characteristics (superoxide dismutase, glutathione peroxidase, total antioxidant activity, and malonaldehyde), proinflammatory cytokines (interleukin-1, IL-1), and immune responses (lysozyme and immunoglobulin M and D) were substantially improved by supplemented feed diets with 1 mg PSE/kg diet, however, tumor necrosis factor was suppressed. Particularly, the OTA levels in the muscle were not detected in the fish group fed OTA-contaminated diets and supplemented with 1 mg PSE/kg diet. Considerably, supplementing OTA-contaminated diets with 1 mg PSE/kg diet considerably improved hepatocytes and hepatoportal pancreas structure, with just a few fatty damaged cells present, and revealed healthy intestinal morphologies. Finally, diets supplemented with 1 mg PSE/kg diet could mitigate OTA's adverse impacts on Nile tilapia growth and health.