Recent attempts to incorporate time to the study of groups reveal temporal factors can impact group functioning. However, studies of group diversity to date are largely cross-sectional and capture the relationship between diversity and its outcomes at one point in time. The present research attempts to overcome this shortcoming by analyzing the interplay between diversity and emotional conflict across time. At the same time, the current study aims to establish an empirical basis for the commonly stated assertion in intergroup relations research that the basis of categorization shifts from surface-level attributes to deep-level attributes as groups mature. Finally, by incorporating shared leadership, this study aims to suggest a contextual lever that can help groups avoid potential disadvantages of diversity. In a longitudinal study of 301 individuals from 81 groups, the present study found that surface-level diversity was negatively linked to emotional conflict in the beginning and the end of groups' interaction whereas deep-level diversity was positively linked to emotional conflict in the middle of groups' interaction. Shared leadership was found to moderate the relationship between diversity and emotional conflict. Implications for human resource management are discussed.