This paper evaluates the payback from efforts of the International Criminal Police Organization (Interpol) to coordinate proactive counterterrorism measures by its member countries to arrest terrorists and weaken their ability to conduct operations. We use Interpol arrest data and data on utilization of Interpol resources by member countries to compute counterfactual benefit measurements, which, when matched with costs, yield benefit-cost ratios. The average of these ratios is approximately 200 over 12 alternative counterfactual scenarios, so each dollar of Interpol counterterrorism spending returns approximately $200. This paper also puts forward a perspective on benefits derived from Interpol’s Stolen and Lost Travel Document database. Interpol provides an inexpensive proactive measure against transnational terrorism that, unlike military operations, does not result in backlash attacks.