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Abstract Tropical wetlands and freshwaters are major contributors to the growing atmospheric methane (CH₄) burden. Extensive peatland drainage has lowered CH₄emissions from peat soils in Southeast Asia, but the canals draining these peatlands may be hotspots of CH₄emissions. Alternatively, CH₄oxidation (consumption) by methanotrophic microorganisms may attenuate emissions. Here, we used laboratory experiments and a synoptic survey of the isotopic composition of CH₄in 34 canals across West Kalimantan, Indonesia to quantify the proportion of CH₄that is consumed and therefore not emitted to the atmosphere. We find that CH₄oxidation mitigates 76.4 ± 12.0% of potential canal emissions, reducing emissions by ~70 mg CH₄m⁻²d⁻¹. Methane consumption also significantly impacts the stable isotopic fingerprint of canal CH₄emissions. As canals drain over 65% of peatlands in Southeast Asia, our results suggest that CH₄oxidation significantly influences landscape-scale CH₄emissions from these ecosystems.