Agaricus bisporus (Lange) Imbach commonly known as white button mushroom, is the most widely accepted food globally with nutritional and medicinal properties. The present experiment was conducted during the Rabi season 2023 - 2024 at Mushroom crop room, Department of Plant Pathology, SHUATS, Prayagraj, Uttar Pradesh to evaluate the effect of tulsi leaf powder at different concentrations (1 %, 1.5 %, 2 %, 2.5 % and 3 %) incorporated into casing mixture (alone and combination) viz., farm yard manure, farm yard manure + cocopeat + sawdust (1:1:1) with an objective to monitor the growth and yield aspects of white button mushroom. Among all treatments used in the study, the results revealed that minimum average time taken for completion of case run (15.14 days) and pinhead initiation (15.57 days) as well as maximum pileus diameter (4.63 cm), stalk length (3.77 cm), stalk diameter (3.01 cm), maximum yield (557.9 g), biological efficiency(12.97 %) and highest cost benfit ratio (1: 3.18) was recorded in farm yard manure + cocopeat + sawdust (1:1:1) + tulsi leaf powder @ 3%. These results indicated that incorporating tulsi leaf powder @3% in casing mixture improves the growth and yield of A. bisporus.