What cause employees in the Australian Public Service (APS) to internally blow the whistle on corruption in the workplace? This research examines the impact of the nature of corruption, organisational culture, and employees’ work attitudes and actions on internal whistle-blowing in the APS. The respondents were found to internally blow the whistle for most types of corruption: fraud, conflict of interest, unlawful disclosure of government information, and perverting the course of justice. Their whistle-blowing behaviour was, however, unaffected by observations of theft of official assets. They were also unlikely to report observations of cronyism and nepotism. Active observers of workplace bullying (those who have blown the whistle after witnessing someone else being bullied) were three times more likely to also internally report corruption than inactive observers of bullying.