Propane dehydrogenation was carried out in hydrogen and steam as reaction media on Pt/MgAl2O4 and Pt-Sn/ MgAl2O4 catalysts. A wide range of Pt and Pt-Sn concentrations was explored. Monometallic Pt catalysts were completely poisoned by steam. Concerning bimetallic Pt-Sn catalysts, tin played an important role related to the activation of platinum particles when the reaction was carried out in steam. On the other hand, tin inhibited cracking reactions leading to an increase of catalysts stability. Activation energy in hydrogen was the same for monometallic and bimetallic catalysts: 22 kcal/mol; while for the reaction in steam, values ranging from 10 to 15 kcal/mol were obtained.