This paper examines the effects of political pressure groups (lobbies) on transboundary emissions of individual countries and on the stability of international environmental agreements to reduce emissions. We consider two types of lobbies, industry and environmentalists, and we allow for asymmetric countries to consider differences in lobby strengths to study strategic international spillovers of national lobby activities. In our model, lobby groups in countries that are non-signatories to the agreement will impact abatement of the lobby’s home country only. In contrast, lobby activities in signatory countries have spillover effects on the abatement decisions of other member countries. As lobby strength impacts abatement, it will, in turn, impact the incentives to participate in the agreement. We find that lobby activities from both lobby groups, industry and environmentalists, can have the potential to facilitate international cooperation to abate global pollution. This, however, depends on the distribution of lobby activities across countries and on whether green lobby groups have a national or international focus.