Oyster mushroom cultivation is an appealing crop for many farmers nowadays as it converts inexpensive agricultural byproducts into a high-value crop. This study investigates the economic viability of oyster mushroom cultivation in East- Siang district of Arunachal Pradesh, with a focus on three randomly chosen community development (CD) blocks i.e. Mebo, Pasighat, and Ruksin. A total of 60 respondents (30 oyster mushroom growers and 30 non-growers) were purposefully chosen. The cost of cultivation has been calculated per five polybag beds, and revealed that small farmers exhibited the highest total cost (` 612.11), followed by medium (` 486.94) and large farmers (` 441.63). However, the largest net return was earned by large farmers (` 506.21) succeeded by small (` 505) and medium (` 493.65). Small farmers paid ` 142.17, medium farmers paid ` 127.02, while large farmers paid `119.89 for producing 1 kg of oyster mushrooms. Notably, small farmers produced the highest yield (4.29 kg per 5-bags). As scale increased, the yield decreased due to the lack of close supervision. The benefit- cost ratio (BCR) calculated as 1.8 for mall farmers, 2.0 for medium farmers and 2.1 for large farmers, hence, larger operations produced higher profits. The study on the resource utilization efficiency indicated that farmers frequently overutilized labour, spawn, paddy straw, and other crucial inputs. The study recommends increasing training andsupport, upgrading infrastructures like cold storages and other post-harvest management facilities, providing improved connections with metropolitan markets, encouraging branding and SHG- FPOlinkages.