CH4 oxidation in Arctic soil plays a crucial role in Arctic CH4 dynamics whereby up to 90% of CH4 produced in soils can be removed. Previous studies have noted the influence of temperature rise on CH4 oxidation, but effects of inorganic nitrogen (N) have been less studied because the Arctic is typically N-limited. However, climate change-induced increases in available N have been reported recently, which may drastically change CH4 oxidation in Arctic soils. Here, we show that excessive levels of soil available N increase net CH4 emissions by attenuating soil CH4 oxidation in Arctic tundra. In-vitro experiments proved consistent with NO3− being responsible for the decrease in CH4 oxidation, leading us to propose that NO3− indirectly inhibits CH4 oxidation by reducing bacterial diversity, a previously unrecognized mechanism. We provide evidence that increased available N can enhance CH4 emissions in Arctic tundra, with profound implications for modeling CH4 dynamics in Arctic.