Together For Us (T4Us) is a newly developed and evidence-informed social identity intervention for youth sport. Drawing on theoretical underpinnings of social identity theory (Tafjel & Turner, 1979) and previous shared leadership intervention research in sport psychology (5Rs; Fransen et al., 2020), T4Us leverages athlete leaders to foster a shared sense of social identity within the team. The purpose of this study was to build off initial feasibility research (McLaren et al., 2021) and conduct a proof-of-concept evaluation to assess whether the T4Us intervention workshop enhanced social identity and to further test the implementation of T4Us. A total of 14 competitive youth soccer teams (Mage = 14.71 years) completed the T4Us intervention at midseason. The proof-of-concept evaluation encompassed multiple components including pretest-posttest social identity perceptions, post-intervention implementation assessment, and qualitative interviews with athletes and coaches. Results revealed that T4Us significantly increased athletes’ perceptions of social identity (t(69) = 3.02, p < .05). Post-intervention implementation evaluation results revealed that the teams used the game plan to support the team trademark, and athlete leaders and coaches encouraged team members to act according to the team game plan (scores > 5 on a 7-point scale). Interviews with athletes and coaches supported the development of greater team identity by engaging in the interactive components of T4Us (e.g., team trademark, game plan). Overall, this proof-of-concept evaluation supports initial feasibility evidence with youth and research in other sport settings, presenting the opportunity to further develop and implement a randomized-controlled T4Us intervention protocol.