Perfectionism or a tendency to aim for an unrealistic standard can impair happiness. However, the potential mechanisms of perfectionism to explain the association between trait emotional intelligence (EI) and happiness are still understudied. This study explores the mediating role of perfectionism in the relationship between trait emotional intelligence (EI) and happiness among young adults. A cross-sectional sample of 259 young adults aged between 18 to 35 years old was recruited. All analyses were conducted using SPSS and AMOS Structural Equation Modeling. High trait EI was linked to low perfectionism and high happiness levels. Furthermore, perfectionism mediated the relationship between trait EI and happiness. Although high trait EI lowered maladaptive perfectionism, the negative impact of maladaptive perfectionism remained and subsequently led to decreasing happiness levels of young adults. This study offers an enhanced understanding of the role of perfectionism in explaining the happiness state of young adults. Moreover, it provides practical implications for using trait EI and managing perfectionism tendency to manage the happiness and wellbeing of the young adult population.