The cap and stalk of Pleurotus sajor-caju mushroom were analysed for proximate composition and used for a 28 day feeding trial in experimental rats. Protein composition of cap (26.33%) and stalk (22.59 %) were relatively high while the crude fat cap (3.67%), stalk (2.6%) was low. Plasma urea of rats fed mushroom cap (25.6±0.3) and stalk (21.7±0.4) were lower than that of the control (31.0±0.3) diet fed rats. The plasma creatinine of rats fed mushroom cap (4.2 ±0.3) and stalk (3.1±0.1) were lower than that of the control (6.9±0.3).Performances of rats fed mushroom showed that daily feed intakes (g) were found to be lower in rats fed mushroom stalk (9.8±0.0) than those fed control diet. Also, daily feed intake was found to be higher in rats fed mushroom cap (10.2±0.0) than the control (9.8±0.0) diet. There were no significant differences in the feed gain ratio of rats fed cap, stalk, and casein control diet. The implication of these results is that mushroom diet is an important source of nutrients which supported growth without eliciting toxicological effects.