Background: Engineering competition teams (ECTs) allow college students to learn about and practice leadership within a technical domain, yet we know little about the mechanisms by which leadership development occurs within these teams. This paper explores how ECT participation contributes to students' leadership identity development (LID). Purpose: This paper addresses the following research questions: (RQ1) How does the ECT experience contribute to students' relational LID? (RQ2) What other factors influence ECT participants' LID? and (RQ3) Does the ECT experience provide opportunities for LID that are different from those provided by other experiences? Design: This paper reports the second phase of a mixed-methods study. ECT members participated in individual semistructured interviews. Transcripts were analyzed via an interpretivist approach using deductive and constant comparative methods. The analysis employed the LID model as the primary theoretical construct. Results: ECTs contributed to most participants' LID. Factors affecting the extent of development included project complexity, team practices related to the claiming and granting of a leadership identity, positional leadership experience, involvement with other organizations, and preconceptions of leadership. Compared with other experiences, ECTs placed more emphasis on leadership based in expertise. Technical competence was considered a key attribute of ECT leaders. Conclusions: ECTs enhanced the LID of most participants, helping them understand leadership as a relational process. The LID model offers promise for designing engineering leadership development programs.