Background and Context: Students' self-efficacy toward computing affect their participation in related tasks and courses. Self-efficacy is likely influenced by students' initial experiences and exposure to computer science (CS) activities. Moreover, student interest in a subject likely informs their ability to effectively regulate their learning in that domain. One way to enhance interest in CS is through using collaborative pair programming. Objective: We wanted to explore upper elementary students' self-efficacy for and conceptual understanding of CS as manifest in collaborative and regulated discourse during pair programming. Method: We implemented a five-week CS intervention with 4th and 5th grade students and collected self-report data on students' CS attitudes and conceptual understanding, as well as transcripts of dyads talking while problem solving on a pair programming task. Findings: The students' self-report data, organized by dyad, fell into three categories based on the dyad's CS self-efficacy and conceptual understanding scores. Findings from within- and cross-case analyses revealed a range of ways the dyads' self-efficacy and CS conceptual understanding affected their collaborative and regulated discourse. Implications: Recommendations for practitioners and researchers are provided. We suggest that upper elementary students learn about productive disagreement and how to peer model. Additionally, our findings may help practitioners with varied ways to group their students.