Nanotechnology has been celebrated as driving a new global industrial revolution that has the potential to harness economic growth and remediate the environment, yet could pose risks to health and the environment. Two of the largest economic actors, the EU and the US, have made very different regulatory decisions toward nanotechnology. The EU introduced an official definition of nanotechnology and created several new nano-specific regulations in recent years, whereas the United States has followed more of a “wait and see” policy. I argue that politics, not technology, best explains the divergence between the US and the EU in creating nano-specific regulations, and I introduce a regulatory regime framework to show why, how, and where politics affect divergent environmental politics. To support this argument, I employ comparative case analysis of the EU and US from 2000 to 2015.