The effect of brine concentration in the range of 10-20%; solution temperature in the range of 35-55oC and duration of osmosis in the range of 30-60 min on water loss (WL) and salt gain (SG) using the response surface methodology at constant solution to sample ratio of 5/1 (w/w) were investigated for osmotic dehydration of button mushrooms. The study was carried out with three variables and three levels Box-Behnken design to optimize input parameters. The brine concentration, temperature of brine and duration of osmosis with respect to water loss and solid gain were analyzed for linear, quadratic and interaction effects. Second order polynomial models were developed using multiple regression analysis, in addition, the adequacy and accuracy of the fitted models were checked by analysis of variance (ANOVA). The response surfaces and contour maps showing the interaction of process variables provided optimum operation as solution temperature of 44.89oC, brine concentration of 16.53% and duration of osmosis of 47.59 min. At this optimum point, water loss and salt gain were predicted to be 40.55% and 2.98% respectively.