Abstract This paper offers an economic case for practical pacifism. Practical pacifism, in contrast to absolute pacifism, recognizes that, while it is possible that state-led war may be justified in some cases, it is extremely difficult to determine if any single instance of war is justified. This leads to a default position of pacifism. Using the tools of economics, we detail the main ways that political institutions are likely to fail and cause harm through warmaking-related activities. Our focus is on the epistemic constraints and incentives facing government actors, as well as the diverse costs and perverse consequences of warmaking. Taking these factors into account strengthens the case for practical pacifism. To date, economists have not engaged the literature on practical pacifism and scholars studying pacifism have not engaged the economic scholarship on political institutions and government failure. Our contribution is to connect the two.