Second Language Acquisition (SLA) is a complex psychosomatic process. As per educational psychology, its acquisition process depends on some affective determinants related to learners' self-confidence that accelerates learners’ zeal of learning the language. However, studies are rare to empirically explore the factors or the ways that help learners build their self-confidence level. Thus, the prime focus of this study is to find out factors associated with accelerating learners’ self-confidence in SLA through a qualitative case study. Data have been collected through semi-structured interviews carried out over the phone due to the COVID-19 pandemic. A total of 13 respondents (7 boys and 6 girls) have been interviewed who have recently completed their postgraduation. The obtained data have been analyzed with the help of the content analysis technique. The study finds that the self-confidence of a learner gets accelerated by three main factors like motivational factor, social factor, and environmental factor which motivate a learner to learn L2. Based on the findings, some policy recommendations have been suggested to further improve L2 learners’ self-confidence level.