This article examines the role of self‐efficacy beliefs in learning English as a foreign language in an Indonesian primary school setting. Self‐efficacy is a significant motivational factor affecting the cognitive and behavioral engagement of learners (Linnenbrink & Pintrich, 2003). The study adopted a mixed‐methods research design that involved the administration of a questionnaire (N = 516), an English proficiency test (N = 516), and a semistructured interview (N = 12). The participants of the study were sixth graders from 12 primary schools in the Indonesian province of East Java. The quantitative findings indicate a relationship between self‐efficacy and language ability, which the interview findings support by pointing to the different cognitive and motivational engagement of the students who held different self‐efficacy levels. These findings provide empirical evidence for the motivational role of self‐efficacy beliefs in language learning. The article ends with practical implications for using EFL instructional processes in the Indonesian primary school context.