mango is an agricultural product of great economic importance for various developing countries, which has increased demand for its nutritional properties and exotic characteristics. the relationship between moisture content and water activity provides useful information for mango processing, especially for drying and storage operations. water activity and moisture content of mango pulp (mangiferaindica l. cv. tommy atkins) were analyzed to determine the sorption isotherms. the water activity was measured using an electric hygrometer at five different temperatures (10, 20, 30, 40 and 50 °c) and wide ranges of moisture content (2.829-0.031 kg kg-1 d.b.) and water activity (0.977-0.215). one theoretical (gab) and four empirical equations (oswin, henderson, halsey and ratti) were used for modeling the sorption isotherms. after following several criteria to evaluate the models, the gab model appeared as the best option to represent the hygroscopic equilibrium of mango pulp (rmse = 0.057, var = 0.996). the sorption isotherms behaved as expected in agro-foodstuffs and similarly with the mango pulp of other cultivars. the isosteric heat of sorptionwas computed using the clausius-clapeyron equation by means of the gab model.a decrease in the isosteric heat of sorption was observed when the equilibrium moisture content increase, with a strong moisture effect at values lower than 0.8 kg kg-1 (d.b.).