We argue that certain provisions of alliance treaties can signal credible commitments to a peaceful relationship among members and establish institutional mechanisms that promote the settlement of disagreements through peaceful negotiation. Nonaggression, peaceful dispute settlement, military institutionalization, and permanent organization provisions should increase the duration of peace between alliance members; we test our hypotheses with a duration model. The analysis generally supports our expectations except that alliances that create permanent organizations, even those specifically established to arbitrate disagreements, are associated with shorter durations of peace. We conclude with some implications of our argument for the study of military alliances and international institutions more broadly.