MoS2 coatings lose their lubricating properties through mechanisms that depend on atmospheric conditions. The tribological performance at the different atmospheres of MoS2 solid lubricant films have been improved by the co-deposition of a small amount of metal. In this study, we investigated the tribological properties of MoS2 co-sputtered with Nb. MoS2-Nb solid lubricant composite film was deposited on AISI 52100 steel substrates and silicon wafers by closed field unbalanced magnetron sputtering (CFUBMS). Composition, morphology and structure were analyzed by a variety of techniques including EDS, SEM, and XRD. The friction and wear properties of air, dry nitrogen, distillated water and oil were determined using pin-on disc tribo-tester. Friction coefficient (COF) and wear rate obtained in dry nitrogen as maximum and in oil as minimum MoS2-Nb films exhibited one type of crystallite orientation and characteristic dense structure. Also there is a sign of the humidity sensitive NbS2 phase which was displayed better lubricating properties in the humid air than in the dry nitrogen conditions. (C) 2008 Elsevier B.V. All rights reserved.