Limited previous research indicates that anaerobic oxidation of methane (AOM) can be an important control over methane (CH4) emissions in freshwater wetlands. We examined the importance of AOM and its response to warming and elevated atmospheric carbon dioxide (CO2) in a whole-ecosystem climate change experiment in an ombrotrophic bog in northern Minnesota, USA. In the first experiment, we sampled plots seasonally and measured rates of net CH4 production or consumption with and without added porewater through the depth profile at in situ temperatures. Net CH4 production occurred in most samples with porewater addition, but net CH4 consumption occurred in most samples without porewater addition, despite being incubated under strictly anaerobic conditions. We hypothesized that these porewater-dependent results were due to the low solubility and initially low headspace concentrations of CH4, which together inhibited rates of AOM when porewater was added. In a second experiment, we directly measured rates of AOM and net CH4 production in the same plots and calculated gross CH4 production during a single sampling event. AOM and gross CH4 production rates were much higher in surface peat, and AOM responded more strongly to warming than CH4 production. Elevated CO2 had minimal effects on any measured process. AOM consumed over 50% of the CH4 produced in some samples, indicating that it is an important process in this bog. Surface soil samples with added porewater also had lower rates of AOM, corroborating the results of the first experiment. Overall, we show that AOM can be an important control over CH4 emissions and their response to climate change in peatlands. Also, laboratory incubations of net CH4 production represent the dual process of gross CH4 production and AOM, and incubation conditions that differentially affect these two processes can provide widely disparate results.