The objective of this paper is to examine the characteristics of leaked-gas dispersion in ship-to-ship liquefied natural gas (LNG) bunkering, thereby providing an insight towards determining the appropriate level of safety zones. For this purpose, parametric studies are undertaken in various operational and environmental conditions, with varying geometry of the ships, gas leak rate, wind speed and wind direction. The study applies computational fluid dynamics (CFD) simulations for case-specific scenarios where a hypothetical LNG bunkering ship with a capacity of 5100 m³ in tank space is considered to refuel two typical types of large ocean-going vessels: an 18,000 TEU container ship and a 319,000 DWT very large crude oil carrier. It is found that wind speed, wind direction, ship geometry and loading condition are important parameters affecting the extent of safety zones in addition to gas leak rate and leak duration. Details of the computations and discussions are presented.