Concentrations of five volatile halocarbons (VHCs), such as chloroform (CHCl₃), trichloroethylene (C₂HCl₃), tetrachloroethylene (C₂Cl₄), chlorodibromomethane (CHBr₂Cl) and bromoform (CHBr₃), in the Northern Yellow Sea (NYS) and Bohai Sea (BS) were determined during spring and autumn 2012. Strong seasonality in VHCs concentrations (except for CHCl₃) were observed. CHCl₃ concentrations were markedly higher (1.5 fold) to coincide with the higher Chl-a concentrations during the spring. While the elevated concentrations of C₂HCl₃, C₂Cl₄, CHBr₂Cl, and CHBr₃ were found matching higher inputs of land runoff during autumn. The VHCs distributions evidently decreased along the freshwater plume from the river mouth ( such as Yellow and Yalu rivers) to the open sea, indicating that distributions of these gases were significantly influenced by terrestrial input and biological activity. Correlation analyses were conducted to investigate possible controls on the concentrations of these gases. In particular, significant correlation was observed only between CHBr₂Cl and chlorophyll a concentrations in the surface seawater during spring, with the tentative conclusion that phytoplankton biomass might not be the main limiting factor of sources of VHCs in the surface sea waters. The sea-to-air fluxes indicated that NYS and BS acted as sources of the gases in the atmosphere during summer and winter.