Decomposition under partial pressure of ammonia of Mo(CO)(6)EMT and subsequent nitridation under flowing ammonia were used to prepare EMT zeolite-encaged molybdenum nitride clusters. The HRTEM and EDS measurements indicate that the final molybdenum phases were homogeneously dispersed, the final clusters’ diameter being less than 10 Angstrom. X-ray diffraction (XRD) patterns and specific surface area measurements showed that the EMT zeolite crystallinity was not affected by ammonia treatments. Ammonia decomposition during the preparation step and X-ray photoelectron spectroscopy (XPS) data allowed us to assess the nitridic nature of the clusters for a nitridation temperature as low as 723 K.