NpOs2 is known to be a ferromagnet with a Curie temperature of 7.5 K. Previous bulk magnetization measurements indicated a field induced magnetization even well below the transition temperature. We have extended this by a measurement of the local high‐field susceptibility, using the Mössbauer effect in 237Np. At 1.6 K, a susceptibility of (1.2±0.2) ×10−2 emu/mole is obtained, in general agreement with the bulk measurement. Such a large susceptibility is best understood by a model of itinerant magnetism, although other properties of the material indicate localized behavior.