Mycoparasites cause serious losses in profitable mushroom farms worldwide. The negative impact of green mold (Trichoderma harzianum) reduces cropping surface and damages basidiomes, limiting production and harvest quality. The goal of the current study was to evaluate new generation fungicides, to devise suitable management strategies against the green mold disease under prevailing agro-climatic conditions. Six non-systemic and five systemic fungitoxicants were evaluated for their efficacy against pathogen, T. harzianum, and host, Agaricus bisporus, under in vitro conditions. Among non-systemic fungicides, chlorothalonil and prochloraz manganese with mean mycelium inhibition of 76.87 and 93.40 percent, respectively, were highly inhibitory against the pathogen. The least inhibition percentage of 7.16 of A. bisporus was exhibited by chlorothalonil. Under in vivo conditions, use of captan 50 WP resulted in a maximum yield of button mushroom of 14.96 kg/qt. So far, systemic fungicides were concerned, carbendazim proved extremely inhibitory to the pathogen (89.22%), with least inhibitory effect on host mycelium (1.56%). However, application of non-systemic fungitoxicants further revealed that fungicide prochloraz manganese 50 WP at 0.1–0.2 percent or chlorothalonil 50 WP at 0.2 percent, exhibited maximum disease control of 89.06–96.30 percent. Moreover, the results of systemic fungitoxicants showed that carbendazim 50 WP or thiophanate methyl 70 WP at 0.1 percent reduced disease to 2.29–3.69 percent, hence exhibiting the disease control of 80.11–87.66 percent. Under in vivo conditions, fungicide myclobutanil at 0.1 percent concentration produced the maximum button mushroom production of 12.87 kg/q.