Norm diffusion promotes the agendas of international organizations worldwide, such as human rights and economic liberalization. Nonetheless, this one-sided narrative overlooks the consequential possibility that bad norms also diffuse in the meantime. This article asks how such reverse diffusion can happen in examining the contagious misreporting of emissions to the United Nations Framework Convention on Climate Change (UNFCCC). I argue that transgovernmental networks enable off-the-record information exchange and thus encourage countries to misreport their emission data––just like what others do––to establish an advantage in international climate negotiations. By applying a forensic analysis to over one million emission records submitted to the UNFCCC and spatial autoregressive regression, I find national governments are more likely to commit misreporting when they have more extensive network connections with those who also misreport. A mechanism analysis further rules out the race to the bottom as an alternative explanation. Through showing that in which way norm diffusion can undermine the functioning of one of the most salient international regimes, this article lends support to the claim that weak enforcement paralyzes global governance. It sheds new light on the diffusion literature and adds to the politics of information manipulation from a spatially dynamic perspective.