Abstract: Pleurotus ostreatus is an edible mushroom rated as the second most important in production in the world after Agaricus bisporus. The local availability of substrates made it an economically viable preposition in the tropics. Sawdust of two selected tropical trees: Hog plum (Spondias mombin, L; Family: Anacardiaceae) and African nut (Pycnanthus angolensis, Welw, Warb; Family: Myristicaceae, were used as the sole substrates for the cultivation of the mushroom. The mineral composition and proximate value of the harvested fruiting bodies were determined, also the toxicological effects on experimental animals (albino rats) was studied. Results obtained showed that the mushroom compared favorably with other food items in terms of its protein quality, carbohydrate and calorific values as it ranges from 7.54±0.14-11.74±0.29%, 43.65±0.32-50.67±0.41% and 273.40±0.16-307.54±0.13 kcal g-1, respectively. The toxicological analysis through histopathological assay also revealed that there was no observable damage on the major organs of the experimental animals fed with mushroom composed diet (sample meal) and soybean composed diet (positive control). However, the organs of the experimental animals fed with protein free diet (negative control) were observed to have necrotic lesion and multifocal lymphocytic aggregates on the liver and kidney. Also, a disruption of the villi tips of the intestine was equally observed.