Tunnel construction are essentially infrastructure projects that includes many interfered and sophisticated tasks. This paper presents a decision support tool, Tunnel_Sim, for planning tunnel construction projects using computer simulation. The proposed tool assists contractors in estimating time and cost, required for the construction of tunnel projects. Five construction techniques are coded in the proposed tool to capture the construction of open/closed rectangular cross-section tunnels and circular cross-section tunnels. The decision support tool divides the construction of tunnels into working zones. It estimates the total duration and cost for each zone. The proposed tool selects the best construction technique from a set of alternatives based on a decision making method that utilizes fuzzy numbers. An application example is presented to demonstrate the characteristics of the proposed Tunnel_Sim.