In recent years, the International Maritime Organization (IMO) has introduced stringent regulations to reduce gaseous emissions from marine diesel engines, targeting sulfur oxides (SOx), nitrogen oxides (NOx), and carbon dioxide (CO₂). Compliance measures include limits on fuel sulfur content, NOx emission standards, and energy efficiency frameworks such as the Energy Efficiency Design Index (EEDI) and Ship Energy Efficiency Management Plan (SEEMP). Within this regulatory context, natural gas has emerged as a promising alternative marine fuel. This thesis evaluates the technological, environmental, and economic feasibility of using natural gas in four-stroke marine compression ignition engines operating in dual-fuel mode. Natural gas combustion enables significant reductions in NOx, CO₂, and particulate matter emissions, while effectively eliminating SOx emissions. However, challenges such as increased unburned hydrocarbon emissions and methane slip—due to methane’s high global warming potential—must be considered. The study combines thermodynamic analysis, experimental data from the literature, and a techno-economic assessment of retrofitting existing vessels. Results indicate that dual-fuel operation is a technically viable and environmentally beneficial solution, although its economic feasibility is highly dependent on fuel price dynamics and retrofit costs.