The benefits of effective leadership practices have often been examined. However, little is known about how these practices impact the perceptions of agency employees regarding whistle-blowing. For instance, only two cross-sectional studies were found to examine an association between transformational leadership (the most often studied leadership practice) and whistle-blowing attitudes. To extend these studies, we examined the relationship between transformational-oriented leadership behaviours and whistle-blowing attitudes using panel data. The findings revealed that transformational-oriented leadership increased the extent to which employees in agencies felt they could disclose wrongdoing without facing retaliation. Transactional-oriented leadership was also found to have a positive effect on these whistle-blowing behaviours; however, the effect size was smaller. The implications of these findings are thoroughly discussed in the article.