A method is presented for making an amino alkoxy-modified silsesquioxane (amino AMS) comprising one or more compounds selected from the group consisting of an amino-AMS, an amino/mercaptan co-AMS, an amino/blocked mercaptan co-AMS, and mixtures of these. The use of solid strong cationic catalysts in this reaction system is advantageous because the catalyst remains as a solid throughout the reaction, allowing simplified separation of the solid catalyst from the soluble amino AMS or amino co-AMS products, resulting in total or near total recovery of the amino AMS or amino co-AMS products, as well as virtual total recovery of the catalyst for recycling. The use of the solid strong cationic catalysts is advantageous because it results in amino AMS products that are free of, or substantially free of, residual acid catalyst.