Palavras chave: Sorghum bicolor L. (Moench), irrigação de pastagem, viabilidade financeira, custos de produção. KIRCHNER, J. H.; ROBAINA, A. D.; PEITER, M. X.; TORRES, R. R.; MEZZOMO, W.; PIMENTA, B. D. ABSTRACTBeef cattle kept in pasture of forage sorghum is characterized as one of the main means of bovine production in Rio Grande do Sul. However, rains are irregulat and producers use irrigation as alternative to the problem. However, there is a need to determine production costs and financial viability of the activity. The objective of this work was to evaluate the financial feasibility of irrigation in forage sorghum for beef cattle for different expectations of average daily weight gain of the animals. Two experiments were conducted in 2015/2016 and 2016/2017 in Santa Maria / RS, and the yields of six conventional irrigation depths (0, 25, 50, 75, 100 and 125% of the ETo) were evaluated, in four replications, and randomized block design. With the productivities, production functions were generated and the possible animal load to be fed for each treatment was determined. Three scenarios were simulated of daily weight gain per animal (0.5, 1 and 1.5 kg-1animal-1day-1), and the production costs for each established water condition, in addition to the financial return for each scenario tested. Financial feasibility has been verified for most of the simulated situations evaluated and costs depend on the precipitation regime.