Whistleblowing is viewed as an effective mechanism to detect and deter corruption. Prior research focused the discussion on whistleblower intention, characteristics, protection, and the consequences of whistleblowing. It overlooked the essence of whistleblowing infrastructure like whistleblowing law and regulations, channels and the person (or department) in-charge of handling the system, as the main prerequisite for a sound whistleblowing system. The current study is the first to explore the current practice of a whistleblowing system among government institutions in Indonesia. The purpose of this study is to explore the current practices of the whistleblowing system in Indonesia; its use and impact for controlling corruption; and various challenges, opportunities and strategies for future improvement. This study analyses primary data obtained through online questionnaires and semi-structured interviews from participants representing government institutions in Indonesia. The sample was selected based on the stratified purposive sampling method. The absence of national policies mandating a whistleblowing system within government institutions, compounded by weak protection and the complex requirement for protection, showed that whistleblowing practices in Indonesia still lag behind other countries. The research results provide an overview of the current practice of whistleblowing systems among government institutions in Indonesia. This includes, among others, the nomenclature of the system, various channels for receiving reports, different perspectives on what constitutes a whistleblowing system, and officials or bodies (usually the Inspectorate General) that will receive the report and follow it up. The results of the study also identified various structures of whistleblowing units in government institutions and discussed the impact of whistleblowing systems on controlling corruption. In this regard, some institutions disclosed their experience of investigating corruption cases that initiate from whistleblowers' reports. Research findings from this study also explore challenges, opportunities and strategies for the development of a whistleblowing system in Indonesia. It argues that it is hard to expect employees and the public to disclose wrongdoings if the reporting channel is not provided, as the law that regulates and mandates the whistleblowing system has not been enacted, and the person or department managing the whistleblowing system may lack the required competences. Research outcomes from this study are expected to encourage the Indonesian government to extend whistleblowing practices in their institutions and strengthen their whistleblowing policies. It also offers recommendations to policymakers, practitioners and academics on optimising whistleblowing systems to reduce corruption. Several ideas for future studies were also identified.