The preparation of NASICON powders has been achieved by sol-gel methods. The precursor solution was either rapidly hydrolyzed, to get a precipitate, or slowly gelated under exposure to atmospheric humidity. The slow hydrolysis process was studied using nuclear magnetic resonance (NMR) spectroscopy in liquid phase. Two-dimensional experiments indicate the occurrence of ligand exchange reactions in solution. Monodimensional 1H, 13C, 31P, and 23Na NMR spectra were also measured. NMR allowed us to follow the advancement of the reaction and determine the degree of polymerization.