As innovative technologies are being deployed to accelerate shipping decarbonization in response to air emission regulations, there is considerable concern about the cost effectiveness of such technologies from a life-cycle perspective. This study conducts a life-cycle cost analysis (LCCA) on an innovative marine dual-fuel engine under uncertainties, comparing the total life-cycle cost performance of such an engine with that of a conventional diesel engine. By proposing several economic Key Performance Indicators (KPIs) such as the Net Present Cost (NPC), the Net Saving (NS) and the Saving-to-Investment Ratio (SIR), the findings indicate that the dual-fuel engine is more cost-effective than the diesel engine under a given fuel price scenario. The uncertainties are meticulously treated by using scenario sensitivity analyses and a Monte Carlo simulation. The scenario sensitivity analyses reveal that the cost effectiveness of the dual-fuel engine is sensitive to the high gas price scenarios. It is uncovered from the Monte Carlo simulation that there is an adequate degree of confidence when opting for the dual-fuel engine. Furthermore, fuel prices are found to be the most influential cost driver. Different foreseeable carbon pricing scenarios are also simulated to show that the dual-fuel engine is still the most favorable option. Regardless of fuel prices and carbon pricing scenarios, the dual-fuel engine provides a considerable environmental benefit with a CO₂ emission reduction potential of 33%. The findings of this study are of interest within the field of shipping investment appraisals and relevant to decision-makers (i.e. ship-owners and investors).