Given the ongoing challenge of high CO2 emissions in the maritime sector and the industry’s effort to reduce its carbon footprint, this study focuses on analysing a practical case involving a Ro-Pax vessel. The research will conduct an in-depth assessment of the Energy Efficiency Existing Ship Index (EEXI) and Carbon Intensity Indicator (CII) examining the key parameters that influence this index and evaluating the vessel’s compliance with the International Maritime Organization (IMO) regulations. Through a comparative analysis, different scenarios will be explored, assessing how EEXI and CII values varies depending on fuels used for propulsion. This study will consider conventional fuels, alternative fuels and energy efficiency measures taking into account the impact of the vessel over the environment and identifying the most optimal strategies to improve the accordance with decarbonization objectives.