The national government has a crucial role to play in combating climate change, yet federal projects continue to constitute a major source of United States greenhouse gas emissions. Under the National Environmental Policy Act, agencies must consider the environmental impacts of major federal actions before they can move forward. But agencies frequently downplay or ignore the climate change impacts of their projects in NEPA analyses, citing a slew of technical difficulties and uncertainties. This Article analyzes a suite of the most common analytical failures on the part of agencies with respect to climate change: failure to account for a project’s downstream and upstream greenhouse gas emissions; failure to acknowledge a project’s effect on the country’s energy mix; and failure to consider a reasonable social cost of carbon. After summarizing current regulatory practice and case law on each topic, this Article finds that despite protestations that accounting for such impacts is infeasible, agencies already possess many of the tools needed to assess such impacts, and indeed, some agencies already use these tools to do so. Furthermore, courts are increasingly holding agencies accountable for a full and fair assessment of climate change effects in NEPA analysis. This Article aims to highlight best practices so that agency offices can learn from one another, fulfill NEPA’s mandate, and begin to provide leadership in the fight against climate change.