The Return-to-Sport (RTS) protocol is recommended for rehabilitating concussed athletes (Patricios et al., 2023). Limited studies exist on psychosocial factors influencing RTS (Bloom et al., 2022). Social support is a psychosocial factor that influences concussion rehabilitation (Kita et al., 2020). We explored nine (n = 7 females, n = 2 males) Canadian university rugby, basketball, and track and field athletes’ (Mage = 21.00, SD = 1.80) social support during RTS through a prospective mixed-methods design. Support agents were identified and ranked using concentric circles maps (Van Waes & Van den Bossche, 2019), the types and degree of support were measured with the Perceived Available Support in Sport Questionnaire (PASS-Q; Freeman et al., 2011) and experiences were explored through two semi-structured interviews. Descriptive and frequency-based analyses were performed on concentric circles maps and PASS-Q data. Codebook thematic analyses were performed on interview data (Braun & Clarke, 2021). Athletes identified 16 agents. Athletic therapists, student trainers, head coaches, significant others, and teammates/friends were most important. Significant others provided the most emotional (M = 2.82, SD = 1.85) and esteem (M = 2.63, SD = 1.85) support. Athletic therapists (M = 1.86, SD = 1.35) and head coaches (M = 0.93, SD = 1.19) provided the most informational and tangible support. Interviews showed support behaviours (e.g., checking-in), contextual factors (e.g., team-norms), concussion and RTS factors (e.g., uncertain timeline), and factors influencing psychological readiness (e.g., fear) impacted athletes’ RTS. Together, results demonstrate social support fluctuates throughout concussion RTS by agent, type, and behaviour.