This article investigates the most important determinants of domestic institutional change in combating corruption and reforming the judiciary in Bulgaria and Romania since EU accession in 2007. It explores how EU and domestic incentives trigger domestic institutional change, and how the two interact with one another. It argues that political leaders and parties will only continue and deepen reforms in response to the twin forces of EU and domestic influence. The EU incentives that shape elite choices stem primarily from public monitoring by the European Commission of government performance and the possibility of sanctions by the EU. The domestic incentives centre on winning elections and holding power, with substantial variation explained in part by diverging sources of domestic support.