This study investigated the sources of self-efficacy of college students enrolled in a learning frameworks course, whom we identified as underachievers. Through weekly journal entries, the group of underachievers (n = 13) cited the factors that made them feel confident or not confident. Students' responses to open-ended prompts were coded according to Bandura's (Self-efficacy: the exercise of control, W.H. Freeman, New York, 1997) four hypothesized sources of self-efficacy and an additional emergent theme of self-regulated learning. After, through student responses on a self-report survey, we compared the group of underachievers to a group of achievers ( n=36) on their self-efficacy and its sources. Both quantitative and qualitative results underscored the importance of mastery experiences for underachievers. The underachievers had significantly less mastery experiences and verbal persuasions despite having similar levels of self-efficacy. Implications for how to cultivate mastery and to provide efficacy-supportive feedback as well as psychological mechanisms regarding high potential underachievers are discussed.