Ongoing ocean warming can release methane (CH₄) currently stored in ocean sediments as free gas and gas hydrates. Once dissolved in ocean waters, this CH₄ can be oxidized to carbon dioxide (CO₂). While it has been hypothesized that the CO₂ produced from aerobic CH₄ oxidation could enhance ocean acidification, a previous study conducted in Hudson Canyon shows that CH₄ oxidation has a small short‐term influence on ocean pH and dissolved inorganic radiocarbon. Here we expand upon that investigation to assess the impact of widespread CH₄ seepage on CO₂ chemistry and possible accumulation of this carbon injection along 234 km of the U.S. Mid‐Atlantic Bight. Consistent with the estimates from Hudson Canyon, we demonstrate that a small fraction of ancient CH₄‐derived carbon is being assimilated into the dissolved inorganic radiocarbon (mean fraction of 0.5 ± 0.4 %). The areas with the highest fractions of ancient carbon coincide with elevated CH₄ concentration and active gas seepage. This suggests that aerobic CH₄ oxidation has a greater influence on the dissolved inorganic pool in areas where CH₄ concentrations are locally elevated, instead of displaying a cumulative effect downcurrent from widespread groupings of CH₄ seeps. An upper limit approximation of the input rate of ancient‐derived DIC into the waters overlying the northern U. S Mid‐Atlantic Bight further suggests that oxidation of ancient CH₄‐derived carbon is not negligible on the global scale and could contribute to deep‐water acidification over longer time scales.