Scholars have argued that whistle-blowing is consistent with public service motivation (PSM), given that whistle-blowing is a form of self-sacrifice and concern for the public interest. Such a connection is also consistent with the Prosocial Organizational Behavior (POB) Model. However, only one article was found that examined the direct association between PSM and whether or not employees reported unlawful acts. Furthermore, no article was found to explore the relationship between PSM, whistle-blowing, and seriousness of wrongdoing—an important intervening factor that influences decisions to report. This is surprising because whistle-blowers can prevent detrimental harm to individuals and society and yet we still know little about the internal motives that cause them to come forward. Consequently, the connection between PSM and whistle-blowing was investigated further in this article. Consistent with the POB Model, PSM was positively associated with whistle-blowing generally, as well as internal and external whistle-blowing. Seriousness of wrongdoing was also found to have a positive effect on whistle-blowing. Furthermore, seriousness of wrongdoing was found to moderate the relationship between PSM and only internal whistle-blowing. The implications of the findings are discussed in the article.