Many of the most significant international treaty negotiations take years, and sometimes decades, to conclude. The international climate negotiations, trade negotiations, and law of the sea negotiations are all examples. Yet, notwithstanding their common occurrence and importance, prolonged international negotiations are not well understood. In these negotiations, state preferences are not fixed, but fluid, as negotiating positions change. This temporal dimension of prolonged negotiations is insufficiently captured by existing theories of international negotiations, which, by virtue of their focus on individual negotiation outcomes at one point in time, tend to be static in their analysis. This article combines an analysis of existing theories of international negotiations with the findings of an empirical study of the climate change negotiations. It reveals a series of internal and external factors distinct to prolonged international negotiations, emphasizes the importance of the temporal dimension, and explains how and why the negotiating positions and the type of agreements states are prepared to sign change over time. Building on these variables, state behavior in prolonged international negotiations can be usefully conceived of as (at different points in time) either an immature or mature game, in which strategic opportunities arise at different phases of the game for networked actors to constructively influence state behavior. Eight strategies are suggested that traditionally weak actors can employ to steer prolonged international negotiations toward their preferred outcome.