During the months leading up to the Rwandan genocide of 1994, cognitive biases obstructed the capacity of U.S. government analysts and policymakers to anticipate mass violence against the country’s Tutsi minority. Drawing on recently declassified U.S. government documents and on interviews with key current and former officials, this essay shows that most U.S. government reporting on Rwanda before April 1994 utilized a faulty cognitive frame that failed to differentiate between threats of civil war and genocide. Because U.S. officials framed the crisis in Rwanda as a potential civil war, they underestimated the virulence of the threat to Tutsi civilians and discounted the risk of catastrophic violence. The “civil war frame” also justified rigid U.S. policy guidance that may have exacerbated ethnic and political conflicts in Rwanda on the eve of the genocide. The phenomenon of faulty cognitive framing remains a challenge for contemporary atrocity prevention and response efforts in countries including Libya, South Sudan, and Syria.