Abstract: While mangroves are regarded as one of the most carbon-rich forests in the tropical and subtropical regions, their soils could at the same time be potential net sources of greenhouse gases (GHGs) such as methane (CH₄) and nitrous oxide (N₂O) owing to frequent flooding by tidal water and considerable nutrient inputs from upland areas. In this study, we characterized the spatial and temporal variabilities, as well as the environmental and biotic controls, of soil GHGs emissions from a subtropical mangrove in Hong Kong through intensive field measurements at monthly intervals over one full year. The average soil CO₂ flux was not significantly different among the three tidal positions of the mangrove (from far to near along the direction perpendicular to the coastline), while that of CH₄ was significantly higher in the middle zone owing to a more anaerobic environment for methanogenesis. A significantly higher mean soil N₂O flux was observed in the landward zone, probably because of the greater organic matter content in soils that stimulated nitrate supply and denitrification. Significant seasonal variations in soil GHGs emissions were also detected in this mangrove, with significantly lower CH₄ flux in winter in response to the low temperature and high salinity that suppressed CH₄ production, as well as significantly higher and lower CO₂ emissions in the summer and winter, respectively, owing to differences in soil temperature and organic matter content that governed microbial activities. Significantly higher mean N₂O flux was found in the middle zone in autumn than the other three seasons, which could be related to the greater supply of soil available nitrogen for N₂O production. Furthermore, we noted significant intra-annual variability of soil GHGs fluxes, with the relative standard deviations of both monthly CH₄ and N₂O fluxes being over 115%. Our findings highlight the need of taking into consideration the high spatial and temporal variability of soil GHGs fluxes in order to have an accurate assessment of the role of mangroves in future climate change.