Abstract: Green mold (Trichoderma spp.) is a devastating disease in the crop production of mushrooms. In India, it has been reported to cause serious crop losses. It is also common contaminant, occurring in mushroom houses in the Kashmir valley. The aim of the present study was to check the in vitro and in vivo efficacy of fungicides against Green mold (Trichoderma harzianum) associated with the cultivation of Pleurotus sajor-caju. Pleurotus sajor-caju is the third most commercially important edible mushroom worldwide. Five fungicides namely Carbendazim, Bitertanol, Hexaconazole, Captan and Mancozeb were evaluated in vitro against Green mold (Trichoderma harzianum) and against the mushroom mycelium as well, by following Poison food technique. The results revealed that the maximum average inhibition of Trichoderma harzianum was recorded in Carbendazim (90.8%), followed by Bitertanol (40.0%), Captan (36.6%) and Hexaconazole (16.1%). The least inhibition (11.7%) of Trichoderma harzianum was exhibited by Mancozeb. It was further observed that Carbendazim exhibited the least inhibition (24.9%) of Pleurotus sajor-caju, followed by Captan (45.5%), Bitertanol (63.0%) and Hexaconazole (74.5%). The maximum inhibition (87.4%) of Pleurotus sajor-caju was exhibited by Mancozeb. Fungicides showing maximum efficacy against the pathogen (Trichoderma harzianum) and minimum efficacy against mushroom (Pleurotus sajor-caju) were further tested against Trichoderma harzianum during an in vivo test in mushroom house. It was observed that all tested fungicides reduced the disease intensity of Trichoderma harzianum and produced more yield than control polybags. Maximum increase in yield (36.9%) over control and minimum mean disease incidence (9.3%) was recorded in treatment which received Carbendazim as the fungicide. Carbendazim was found to be best fungicide, against the infection of Green mold (Trichoderma spp.) disease of mushrooms.