Recent quantitative research has begun to model peace agreement content. However, very few studies examine how mediators shape individual agreement content and peace accord comprehensiveness. The most recent contributions use latent variable models to scale agreements statistically according to their comprehensiveness. Although this research considers mediation as a predictor of comprehensiveness, it comes to the surprising conclusions that mediators seem to reduce the comprehensiveness of agreements. However, it offers no substantive theoretical explanation for this result. We address this gap and develop a theoretical argument, which argues that mediators do far more than “ripen” the conflict and shape agreement comprehensiveness. Additionally, mediators structure negotiations, set the agenda, and prioritize some topics while strategically postponing others. Whether and when an issue is part of the negotiation depends on the ripeness of the negotiation situation and the characteristics of the specific issue. We hypothesize that mediators facilitate compromise on the most difficult and controversial topics and increase the likelihood that these topics are included in the agreement. Hence, mediators shape individual content and not just conflict parties’ ripeness for a comprehensive agreement. We draw on data of the UCDP Peace Agreement Dataset and the PA-X Database to model and test our theory.