Abstract Dynamic nuclear polarization surface enhanced NMR (DNP‐SENS), Mössbauer spectroscopy, and computational chemistry were combined to obtain structural information on the active‐site speciation in Sn‐β zeolite. This approach unambiguously shows the presence of framework Sn IV ‐active sites in an octahedral environment, which probably correspond to so‐called open and closed sites, respectively (namely, tin bound to three or four siloxy groups of the zeolite framework).