The study was conducted to analyze the influence of yield and economic viability of tomato (Solanum lycopersicum Mill) under varietal replacement demonstration in Bhagalpur District, Bihar, India during Rabi 2018-2019. Varietal adoption demonstrations were conducted on tomato by the active participation of the farmers. The improved technologies consist disease resistant variety (Kashi Vishesh), balanced fertilizers (Soil test based) application and integrated pest and disease management, etc. (All the recommended practices were provided to the selected farmers. The data related to the cost of cultivation, production, productivity, gross return and net return were collected as per scheduled and analysed. Results of the study revealed the higher yield in the demonstrations was recorded (498 q/ha) as compared to farmers practice traditional adopted by the farmers (396 q/ha). The percentage increase in the yield over farmer’s practice 25.75 was recorded. The technology gap, extension gap and technology index were computed 132 q/ha, 102 q/ha and 20.95% respectively. The demonstrated field gave higher net return Rs. 4, 02,000/- and B: C ratio and incremental demonstrated B: C ratio is 1: 4.12 and 1: 5.18 respectively. The result of the study indicated the gap existed in the potential yield and demonstration yield is due to soil fertility and weather conditions. Present results clearly show that the yield and economics of tomato can be boost up by adopting recommended technologies.