Abstract: Research on UN peacekeeping operations has explored different sources of heterogeneity between missions, showing how deployment size and personnel composition affect peacekeeping outcomes. So far, however, there is no systematic data allowing scholars to evaluate whether variation in mandated tasks influences peacekeeping effectiveness. Similarly, we know very little about the political negotiation process behind the different configurations of missions’ mandates. This article presents an original dataset of peacekeeping mandates that will allow researchers to explore novel avenues of research about peacekeeping as (i) a conflict resolution tool and (ii) an international institution. Instead of relying on the binary distinction between traditional and multidimensional missions, the PEMA Dataset identifies 39 distinct tasks and three modalities of engagement at two different strengths, coding initial mandates as well as extensions and revisions. The data shows that recent peacekeeping missions are more complex than before and experience considerable changes over their lifecycle. To illustrate the usefulness of our data, we re-examine Hultman et al.’s (2013) analysis of missions’ ability to protect civilians and show how host government and rebel groups respond differently to the content of mandates and the number of armed peacekeepers.