Labor unions are a mechanism for employee advocacy, but their role in surgery resident wellness is poorly characterized. To understand experiences with unionization among general surgery residents and residency program faculty and staff. This exploratory qualitative study included data from the Surgical Education Culture Optimization Through Targeted Interventions Based on National Comparative Data (SECOND) trial. In the exploratory phase of the SECOND trial (from March 6, 2019, to March 12, 2020), semistructured interviews about wellness were conducted with residents, faculty (attending physicians), and staff (program administrators) at 15 general surgery residency programs. Unionization was identified as an emergent theme in the interviews. Data analysis was performed from March 2019 to May 2023. The main outcome was resident and faculty experience with resident labor unions. In the qualitative analysis, lexical searches of interview transcripts identified content regarding resident labor unions. A codebook was developed inductively. Transcripts were coded by dyads, using a constant comparative approach, with differences reconciled by consensus. A total of 22 interview transcripts were identified with relevant content. Of these, 19 were individual interviews conducted with residents (n = 10), faculty (n = 4), administrative staff (n = 1), a program director (n = 1), a department chair (n = 1), and designated institutional officials (n = 2), and 3 were from resident focus groups. Residents from all postgraduate year levels, including professional development (ie, research) years, were represented. Interviewees discussed resident unions at 2 programs (1 recently unionized and 1 with a decades-long history). Interviewees described the lack of voice and the lack of agency as drivers of unionization ("Residents…are trying to take control of their well-being"). Increased salary stipends and/or housing stipends were the most concretely identified union benefits. Unanticipated consequences of unionization were described by both residents and faculty, including (1) irrelevance of union-negotiated benefits to surgical residents, (2) paradoxical losses of surgery department-provided benefits, and (3) framing of resident-faculty relationships as adversarial. Union executives were noted to be nonphysician administrators whose participation in discussions about clinical education progression may increase the time and effort to remediate a resident and/or reduce educators' will to meaningfully intervene. Active surgical resident participation within the union allows for an understanding of surgical trainees' unique needs and reduced conflict. In this qualitative study, unionization was a mechanism for resident voice and agency; the desire to unionize likely highlighted the lack of other such mechanisms in the training environment. However, these findings suggest that unionization may have had unintended consequences on benefits, flexibility, and teaching. Effective advocacy, whether within or outside the context of a union, was facilitated by participation from surgical residents. Future research should expand on this exploratory study by including a greater number of institutions and investigating the evolution of themes over time.