The aim of the research is to explore the influence of overseas workers’ cultural intelligence on their in-role job performance and career engagement. The research will also help to understand interactions among variables including cultural intelligence, career engagement, and in-role job performance. Based on samples from those Taiwanese who work in Vietnam and responding to the current trend of Taiwanese going to Southeast Asia for jobs, this research is to provide a meaningful reference for human resource management of overseas workers in Southeast Asia. A total of 218 valid samples were collected via an online survey. Data were analyzed by using SEM (Mplus 7.0). Analysis results indicate that cultural intelligence has a significant positive effect on both in-role job performance and career engagement. At the same time, in-role job performance has a significant partial mediating effect on the relationship between cultural intelligence and career engagement. Based on the research results, we concluded that cultural intelligence and in-role job performance have an important influence on one’s career engagement. In addition, cultural intelligence can influence one’s career engagement through the mechanism of in-role job performance. Finally, based on the research results, this study proposes practical management methods for managers and gives recommendations for future research.