We employed spin-polarized density functional theory to study the bonding and dissociation of NH(3) and its fragment on a nanosized icosahedral Fe(55) cluster. The site-preference investigations, suggest that for NH(3), only the interaction perpendicular to the cluster is favorable (-0.37 eV < B.E.(NH(3)) < +0.05 eV). Stable geometries of N and H on the high symmetry adsorption site of Fe(55) have been calculated as well. Both of these atoms have similar behavior: only the hollow or top sites are stable. Possible dissociation paths of the NH(3) to atomic nitrogen and hydrogen were identified. The calculated lowest reaction barrier for the overall process is 1.48 eV. The rate limiting step is the first hydrogen removal from the NH(3). Our results suggest that the catalytic activity of iron surfaces towards ammonia-like molecules is enhanched when the metal is in the nanostructured phase. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.