In light of the deleterious consequences associated with workplace bullying, it is important to identify the work-related factors that can contribute to the presence of bullying behaviors over time. Up to now, most research on the topic has investigated job characteristics (presence of job demands, absence of job resources) as contributing factors of workplace bullying. Given the key role leadership plays in shaping employees' work environment, this study aims to better understand how harmful forms of leadership relate to bullying behaviors over time and, subsequently, to employee functioning. More specifically, this longitudinal study (two data collections over a 3-month period) conducted among a sample of Canadian employees (T1 n = 600, T2 n = 422) assesses the temporal relationship between tyrannical leadership, exposure to bullying behaviors, and turnover intention, as well as the moderating role of perceived coworker support in the relationship between tyrannical leadership and bullying behaviors. Results from cross-lagged analyses show that, controlling for baseline effects, T1 tyrannical leadership positively predicts T2 exposure to bullying behaviors and that T1 bullying behaviors positively predict T2 turnover intention. T1 coworker support did not significantly buffer the relationship between T1 tyrannical leadership and T2 exposure to bullying behaviors, although it did significantly predict, negatively so, T2 turnover intention. The present study provides valuable insight into the social contextual determinants of bullying behaviors and highlights the destructive nature of tyrannical leadership. Furthermore, this study illustrates the importance of fostering supportive behaviors between colleagues, as this important social resource can play a key role in reducing turnover intention over time.