This paper reports on the role of personality as an antecedent of proactive behaviour at work in the form of whistleblowing. In the interest of triangulation, two studies were used, along with two personality measures. The results of Study 1, conducted among 503 municipality employees, show that the NEO Five-Factor Inventory dimensions of extraversion and agreeableness are significantly associated with whistleblowing, with odds ratios of 1.13 and 0.91, respectively. The result from Study 2, conducted among a representative sample of employees, shows that the circumplex of interpersonal problems dimension domineering was significantly associated with whistleblowing, with an odds ratio of 1.66. The results suggest that personality, in the form of high extraversion and dominance and low agreeableness, do play a role as antecedents of whistleblowing.