Natural-gas supply chain network (NGSCN) includes production, transmission, and distribution stages, numerous types of exogenous and undesirable inputs, intermediate products, and outputs. These lead to a complicated structure for NGSCN. Measurement of efficiency of NGSCN is essential and important. In this paper, network data envelopment analysis model is developed to measure the efficiency of the natural-gas supply chain in Iran. The main properties of the proposed model, i.e., feasibility and bound of the objective function, are discussed through several theorems. The proposed model is used to measure the efficiency of a gas supply chain and the associated efficiency of all elements in the chain during a 5-year planning horizon incorporating real monthly operational data. The results illustrate the total efficiency score of the NGSCN and the efficiency and inefficiency of the production, transmission, and distribution stages. The proposed model of this study can be customized and applied in other energy supply chains such as water, oil, electricity, and wind.