The development of liquefied natural gas (LNG) carrier ships is increasing rapidly along with the demand for alternative energy sources. This study aims to analyze the performance of an LNG-fueled propulsion system for a small-scale LNG carrier ship with a combination gas-electric steam turbine system (COGES). The performance of the propulsion system is analyzed based on the power output generation and the environmental effect of the system. The total power output was evaluated using thermodynamic analysis and the environmental impact was measured by carbon emissions using the life-cycle assessment approach. The analysis results show the COGES propulsion system potentially generates total power of 7600 kW at peak load. The desired ship operational speed of 12 knots can be achieved at 24% load of the total power output. The COGES propulsion system also indicates a low emission than other systems with a carbon emission is 0.149 kgCO2/kWh.