Oil spill incidents with tankers, port terminals and offshore platforms impact seriously on marine life and socio-economic services. They occur more and more frequently and require immediate and effective response which starts with good knowledge of the likely pathways of spilled oil in the region where a pollution has occurred. The drift of a hypothetical oil spill from the main oil port in Peter the Great Bay (PGB) in the Sea of Japan is simulated from a Lagrangian point of view based on the retrospective velocity field of the ROMS circulation model with horizontal resolution of 600 m. The particle-tracking experiments with the effects of oil evaporation and biodegradation have been performed releasing hourly passive tracers at the beginning of every month during a few years. These numerical experiments showed pathways of spilled oil in different seasons, size of the open-sea area covered by the oil and risks of coastline contamination. Three main scenarios of propagation of the spilled oil in the surface layer have been found and analyzed. In the first one, the spilled oil drifts fast away from the coast due to prevailing north/northwest winds in the cold season (from December to April). The second scenario predominantly occurs in the warm season (from May to November) with prevailing south/southeast winds when the oil slick remains near the coast in the first days after an incident. The third scenario is an intermediate one with the dispersal of the spilled oil away from the coast but not too far from the oil spill site. To explain this behavior, we used the Lyapunov maps which allowed us to identify Lagrangian fronts in the study area that shape passive tracer evolution. As a Lagrangian front moves, the oil slick moves with it. At the same time, the front acts as a transport barrier preventing cross-frontal spreading of oil.