Coprinus cinereus is a wild edible and medicinal mushroom available in Tanzania. Methanolic extracts were prepared from whole young and immature mushrooms and the effect of eight different post harvest treatments on nutritional content, antioxidant component and scavenging activities on DPPH (1, 1-diphenyl-2-picrylhydrazyl) radicals were studied. Result showed that Coprinus cinereus fruit bodies are good source of antioxidant and proteins although post harvest treatments had profound effects, which varied significantly at (p<0.05). The highest scavenging ability (LD 50 = 0.119) was found from mushrooms sun dried for 5 days followed by (LD50= 0.133) recorded from young and immature mushrooms (control) while the least (LD50=4.24) was obtained from mushrooms dipped in boiling 10% salt water for 1minute. On the other hand, crude protein ranged between 7-26% with highest and lowest obtained from oven dried and boiled in 10% salt for 1 minute, respectively. For total flavonoid (mg RE/g) the highest value was obtained from control (44.7) followed by (41.13) recorded from oven dried mushrooms. The total phenolic (mg GAE/g) content and vitamin C (mg/100g) varied concurrently with same treatments. They were both higher in mushrooms dehydrated with silica gel (174.77) and (175.18) and lower in mushrooms dipped in boiling water for 5 minute (59.49) and (20.17), respectively. These findings demonstrated that Coprinus cinereus is a good source of protein and antioxidant and the best post harvest method is sun drying in which, not only the shelf life of the mushroom increases but also they retains most of good qualities including improved scavenging abilities.