Researchers examined six undergraduate pre-engineering majors' self-regulatory behaviours, ability to self-regulate, self-efficacy beliefs, and intentions to persist using a qualitative methodology. The data collection procedure relied heavily on interviews focusing on participants' engineering interests, beliefs in their abilities to successfully complete an engineering degree, beliefs in their ability to self-regulate, sources of self-efficacy, and self-regulatory behaviour. Through transcription analysis, coding, and cross-coding processes, our findings indicate that the triadic and cyclical nature self-regulation was fundamental to pre-engineering majors' persistence. Students' prior mastery experiences, beliefs in their ability to self-regulate, vicarious experiences, and verbal persuasions contributed to students' self-efficacy beliefs and engineering interests. Time management, prioritising, help-seeking behaviour, knowing professors' expectations, and critical self-evaluation were essential behaviours for pre-engineering students' persistence.