Polarization in the United States and around the world is of growing concern. Polarization is about more than just differences in opinions in society. It occurs when groups increasingly diverge in either actual or perceived differences in opinion and can involve both disagreements about issues and negative views of other groups. Since most environmental problems are collective action problems, polarization may interfere with the kinds of deliberation and collaborations needed for effective environmental decision-making. In this review, we examine how polarization influences environmental decision-making and what strategies could be useful for preventing or reducing the negative consequences of polarization. Evidence about the extent of polarization among citizens suggests the current situation may be less severe than is sometimes assumed. The coevolution of individual views, network interactions, and social media that cause polarization is complex and subject to rapid change. However, there are interventions that seem to be effective at reducing polarization.