While small island developing states (SIDS) are micro-contributors to anthropogenic climate change, they are among the most vulnerable to its impacts, with some islands even facing the possibility of extinction. Recognising their vital stake in an effective climate regime, small island states formed a negotiating group, the Alliance of Small Island States (AOSIS), to represent their interests in the international climate negotiations. Given their limited power, however, to what extent, and by what means, did AOSIS impact the climate regime? Assuming that both the process and outcome of negotiations depend largely on power, this article argues that low-power parties can nonetheless exert influence in international negotiations by ‘borrowing’ power, that is, by drawing on external power sources. A framework for analysis is thus developed and used to assess AOSIS's negotiating strategies and respective successes in the climate change regime from 1990 to 1997. As the analysis reveals, AOSIS made use of external sources of power over this period, and shaped the negotiations to a remarkable degree, much more so than the a priori power distribution would predict.