Institutional innovations in conflict management have received considerable academic attention in the past decades. Yet few studies have considered the design of referendums in peace processes and the role of popular mandates in catalysing negotiated settlements. Drawing evidence from divided societies, particularly the contrasting cases of South Africa and Cyprus, the article points to the importance of ratification sequence and early mandate referendums. Specifically, it demonstrates how mandate referendums focusing initially on domestic constituencies enable leaders to pre-empt ethnic outbidding challenges while concluding a peace agreement. An early ratification process could safeguard the peace process from unavoidable reversals in public opinion, increase flexibility as to the timing of critical decisions and maximise the credibility of leaders aiming for a negotiated settlement. The study of mandate referendums has important implications for broader research on international mediations since it suggests mechanisms by which political actors could ensure the ratification of significant treaties in global or regional politics.