Deadwood plays an important role in mangrove carbon dynamics, yet its contribution to greenhouse gas fluxes remains insufficiently characterized, particularly in Amazonian coastal forests. CH4 and CO2 effluxes were evaluated from dead wood across contrasting salinity conditions on the Ajuruteua Peninsula, considering decomposition class, wood traits, and elemental composition. Marked spatial variation in gas emissions was observed between sites, with salinity exerting a strong inhibitory effect on both CO2 and CH4 release. Differences across decay classes reflect shifts in moisture content and C:N ratios, highlighting the biochemical transformations that accompany progressive decomposition. Species identity did not consistently affect gas efflux, but wood size and decomposition level did contribute to the observed patterns. Elevated CH4 emissions in advanced decay stages underscore the relevance of microbial activity in deadwood-mediated fluxes. These findings emphasize the need to integrate deadwood processes into mangrove carbon budgets, particularly under changing hydrological and climatic regimes.