By studying the ammoniation of the silicoaluminophosphate-type zeolites H-SAPO-34 and H-SAPO-37 by in situ H-1 and Al-27 MAS NMR under continuous-flow (CF) conditions, a two-step adsorption process was determined. The first ammoniation step consists of an adsorption of ammonia exclusively at Bronsted acidic bridging OH groups (SiOHAl), leading to the formation of ammonium ions (NH4-form). The second ammoniation step, which occurs at a higher ammonia coverage, consists of a coordination of ammonia molecules to framework Al atoms in equivalent toP-O-Alequivalent to bridges. This second adsorption step causes a change of the aluminum coordination from a tetrahedral coordination to an octahedral coordination. The ammonia coordination to Al atoms is reversible when the material is purged at 413 K. The hydration of NH4-form silicoaluminophosphates (ammoniated bridging OH groups) causes a coordination of water molecules exclusively to Al atoms in equivalent toP-O-Alequivalent to bridges, leading to a hydrolysis of the framework. Therefore, a hydrolysis of the silicoaluminophosphate framework is hindered if the bridging OH groups (SiOHAl), as well as the aluminophosphate framework (equivalent toP-O-Alequivalent to), is covered by ammonia. The latter may support the stabilizing effect of preloaded ammonia on H-form silicoaluminophosphates toward hydration and weak hydrothermal treatments, as recently observed for H-SAPO-34.