© 2021 Elsevier Inc. Focusing on self-initiated expatriates (SIEs), this study examined confidence in a second language and motivational cultural intelligence or quotient (motivational CQ), to assess their effects on workplace interactions and cultural adaptation. It extended the theory of self-efficacy to cross-cultural settings in which SIEs achieve high levels of performance. The study was conducted with two groups of SIEs based in the United Arab Emirates, whose multicultural workforce often uses English as their workplace language. One group consisted of Chinese SIEs who used English in the workplace. As this was not their first language, their confidence in their English language skills was potentially an issue. The other group consisted of SIEs whose first language was English, and who were therefore using their native language at work. The findings suggest that the language confidence and motivational CQ of SIEs serve as inner drivers and mediators of the relationship between self-efficacy and task performance.