In Tanzania wild edible mushrooms collected during the rainy season have broad cultural acceptance and constitute a traditionally very important nutritious food. However, their assessment as food, which is based on their chemical analysis, has not been adequately studied and documented. The objective of the study was to determine the proximate nutritive potential of three indigenous edible wild mushrooms namely Coprinus cinereus, (Schaeff) S. Gray s.lat., Pleurotus flabellatus, (Berk and Br.) Sacc. and Volvariella volvaceae (Bull.ex.Fr) Singer, grown on composted solid sisal decortication residues. Standard procedures were used to determine the proximate chemical composition of dried samples of domesticated indigenous edible wild mushrooms. Atomic absorption spectrophotometry was used to determine the mineral element composition. The results were compared using an analysis of variance test. There were significant differences in the proximate nutritive values of the three edible mushrooms (p>0.05). Despite differences in the chemical composition of the three indigenous edible mushroom species, the overall nutritional potential of the three mushroom species was quite good. Furthermore, the overall results indicated that the fruit bodies of the three native mushrooms studied have nutrient qualities similar to other cultivated exotic edible mushrooms, and a higher protein content than many cereals and vegetables. The results on a dry weight basis demonstrated significant amounts of protein, vitamin C and minerals, ranging from 17-28 %, 33-55 mg/100g and 5.2-3232 mg/100g, respectively. Furthermore crude fibre ranged between 6.6-11 % and carbohydrate, at 50-62 %, both of which were found to be relatively high. All three species were low in fat content, with a range of 1 to 3.3 %, and energy value (calculated), 302-313 kcal/100g. These results indicated that the studied mushrooms have good nutritive value for human beings. The fact that the domesticated mushrooms were grown using locally adapted biotechnology increases the likelihood of their incorporation in the diet as a food item contributing protein, vitamin C and mineral nutrients. The high crude fibre and low fat content are also important from a nutritional perspective. The researchers believe that it would be appropriate to popularise the utilization of the three mushrooms as unconventional protein rich food sources to supplement the traditional cereal Tanzanian based diet, aimed at combating the problem of protein malnutrition in Tanzania in particular and in developing counties in general.