Summary The influence of different osmotic solution pretreatments (sucrose and glucose with concentration of 45%) on desorption isotherms and glass transition temperatures (Tg) of mango was investigated. The Peleg model satisfactorily described the relationship between water activity (aw) and moisture content of all samples (0.992 < r2<0.997). The equilibrium moisture content of mangoes osmotically pretreated in sucrose was higher than that of samples pretreated in glucose. Differential scanning calorimetry was used to measure the Tg of samples equilibrated with different aw (0.12–0.75). The dependence of Tg on moisture content was adequately fitted by Gordon–Taylor model (0.946 < r2<0.949). The osmo‐dehydrated mangoes showed lower Tg than fresh samples at the same moisture content. Additionally, the samples osmotically pretreated in glucose showed the lowest Tg value. Osmotic dehydration applied to fruits before drying removes water from tissues, whereas the solute enters the foods. Sorption isotherms and the glass transition temperature were determined to provide valuable information on the effects of moisture content on the water availability in foods and on the physical state of food solids.