What explains the move of Jordan to a proportional representation (PR) electoral system in 2016 but not in 2012? This is puzzling given the high public pressure for electoral reform in 2011–12 in the wake of the Arab uprisings compared to 2016. Applying veto player theory to Jordan, this article argues that the non-adoption of PR in 2012 and the subsequent move to PR in 2016 lies mainly in the regime’s perceived uncertainty associated with the results of elections. In 2012, it was feared that elections under a PR system would replicate the 1989 opposition-dominated parliament. The regime, therefore, opted for a mixed system by complementing the single non-transferable vote system with a national party list. To justify such a system, compared to the demanded PR system, the regime resorted to rhetoric directed at both elite and mass levels. In 2016, however, the uncertainty associated with adopting a PR system ceased to exist. The fragmentation of Jordan’s strongest opposition group, the Jordanian Muslim Brotherhood, reduced uncertainty about their electoral strength. At the same time, malapportionment reduced uncertainty regarding the outcomes of the elections. The article shows how electoral reform in authoritarian regimes, as in some democracies, can be explained through the perceived uncertainty of elections’ outcomes.