Conflict, cronyism, and a flawed privatization process damaged Croatia’s international image during its first decade of independence from Yugoslavia. After a change in government in 2000, a parliamentary consensus formed around the pursuit of European integration, but the European Union demanded real progress in tackling corruption, echoing citizen concerns. In response, the Croatian government created a specialized prosecution service called USKOK, the Bureau for the Suppression of Corruption and Organized Crime, to work in concert with other anti-corruption institutions. At first under-resourced and ineffective, USKOK grew in authority and stature after 2005, aided by new legal powers and new leadership. By building capacity and institutional partnerships at home and abroad, USKOK rose to be one of Croatia’s most-trusted government institutions. By 2012, USKOK had achieved a conviction rate surpassing 95%, successfully prosecuting a former prime minister, a former vice president, a former top-level general, and other high-level officials. By turning a corner on corruption, USKOK’s work strengthened the rule of law and cleared a key obstacle from Croatia’s path to European Union accession. This case study describes how USKOK’s leadership built capacity, public trust, and sustainability under pressure.