A series of synthetic microporous analogues of the mineral nenadkevichite, with Ti/Nb molar ratios ranging from 0.8 to 17.1 and a purely titaneous sample, have been prepared. The microporous titanosilicate ETS-4 has been found to be a precursor in the synthesis of synthetic nenadkevichite. The structure of nenadkevichite materials has been extensively characterized by scanning electron microscopy, powder X-ray diffraction, Raman spectroscopy, diffuse-reflectance ultraviolet spectroscopy (DR-UV), and Na-23, Si-29, and Nb-93 high-resolution solid-state NMR. In accord with the published structure for the mineral nenadkevichite, DR-UV and Nb-93 solid-state NMR suggest that titanium and niobium are in distorted octahedral coordination. Raman spectroscopy clearly shows the framework substitution of titanium for niobium. Tn addition, due to stronger dipolar interactions, the replacement of Ti-47 and Ti-49 (diluted quadrupolar nuclei) by Nb-93 (abundant quadrupolar nucleus) results in a significant decrease in the Si-29 spin-spin (T-2) NMR relaxation times. The Si-29 NMR spectra are strongly dependent on the cations present and on the state of hydration of the nenadkevichite materials.