In recent years, educational practitioners have become more aware of the importance of cultivating students' social and emotional skills, in order to facilitate adaptation beyond academic contexts. Emotional intelligence (EI), the ability to regulate one's own and others' emotions appropriately, has often been targeted in educational interventions. Previous studies suggest that EI promotes various positive social outcomes such as social support, prosocial behaviour, and subjective well-being. However, a growing body of research has also shown that EI may sometimes lead to antisocial behaviours such as indirect aggression and support for others' retaliation, but this "darker side" of EI tends to be overlooked. We argue that emotional intelligence without empathy can bring about manipulative or aggressive behaviour, and highlight the need to explore further how EI interacts with other personality traits in determining different social outcomes. This review addresses both the "bright" and the "dark" side of EI, aiming to offer a comprehensive, balanced perspective on its adaptive functions. Based on Reinforcement Sensitivity Theory (RST), our paper proposes that there might be a common mechanism by which EI links to both prosociality and aggression. Our analysis leads to the conclusion that researchers need to elaborate on the motivational mechanism underlying the behaviours of emotionally intelligent individuals, while teachers would be well-advised to pay attention to the motivations that support students' socially adaptive behaviours.