The Dez-Qomroud Tunnel Project lot No. 6 is situated along the Zagros Mountains in west-central Iran. A comprehensive engineering geological study was conducted to determine geomechanical characteristics of the rock masses along the tunnel route. Rock mass classification systems such as rock mass rating (RMR), Q-tunneling index, rock quality designation (RQD), geological strength index (GSI) and rock mass index (RMi) were all employed to classify and characterize the rock masses in order to provide a basis for estimating deformation and strength properties, to supply quantitative data for the design engineering team, and to provide a platform for communication between exploration, design and construction groups. Results obtained from applying different rock mass classification systems for the different rock masses exposed at the QTP6 tunnel path are shown and interpreted in this article.