<p>Coastal ecosystems are ubiquitous sources of methane (CH₄) - a greenhouse gas with 27 times the global warming potential of carbon dioxide. Studies in temperate and subtropical systems show that in addition to tidal cycles, coastal CH₄ dynamics can also be influenced by groundwater exchange. However, the role of tidal pumping and groundwater exchange in CH₄ variability in tropical systems is poorly understood. Here, discrete measurements of CH₄ concentration were combined with a suit of environmental variables and groundwater isotopic tracer (²²²Rn) in a tropical creek across different tidal stages during two contrasting seasons. Surface water CH₄ concentration varied widely during post-monsoon (0.09–0.51 µmol L^− 1) and pre-monsoon (0.01–0.31 µmol L^− 1) periods and negatively correlated with tidal height. However, salinity-CH₄ relationship during the post-monsoon was positive in the surface water, while salinity and ²²²Rn relationship were negative in the porewater suggesting recirculated groundwater as the major CH₄ source. In contrast, the pre-monsoon salinity-CH₄ relationship was negative for the surface water with a positive correlation between ²²²Rn and CH₄ concentrations indicating overreaching influence of fresh terrestrial groundwater. These results show that although tidal pumping is the dominant source of CH₄, shift between recirculated saline and fresh terrestrial groundwater determines pattern of CH₄ variability across seasons. Furthermore, tropical Cyclone Mocha during the pre-monsoon elevated surface water CH₄ concentration from 0.12 ± 0.02 µmol L^− 1 (pre-cyclone) to 0.20 ± 0.01 µmol L^− 1(during the cyclone). Together, this study demonstrates that multiple factors - including tidal pumping, submarine groundwater exchange, and cyclones - act in tandem to regulate CH₄ dynamics. Thus, these drivers must be considered while predicting CH₄ concentrations and emissions in tropical tidal creeks.</p>