Context: Mentorship has been identified as a primary organizational socialization tactic and has been directly associated with transition to practice. Objective: Understand how the mentoring relationship develops for the newly credentialed athletic trainer during the first year of clinical practice. Design: Grounded theory. Setting: Athletic training practice settings. Patients or Other Participants: Thirteen athletic trainers, who graduated from a professional master's program, certified between February and July of 2016, and obtained employment between July to August of 2016, participated in this study (6 female, 7 male, 26 6 [plus or minus] 3 years; work settings included professional sports, college, secondary and middle school, and clinic). Data saturation was met. Main Outcome Measure(s): Semistructured phone interviews were conducted with all participants during 3 specific time points (3, 8, and 12 months posthire). All interviews were transcribed verbatim and coded following the steps of a grounded theory study. Credibility strategies included researcher triangulation and peer review. Results: All 13 participants recognized a mentor, someone who they believed serve in a mentoring capacity during their transition into clinical practice as a newly credentialed athletic trainer. The development of the mentoring relationship for the newly credentialed athletic trainer appeared to be characterized by (1) identification of a mentor who had experience and knowledge, (2) a recognition of the need to have support and continued avenues for growth as a health care professional, (3) an informal initiation of the relationship through a professional relationship by the mentee, and (4) communication that overtime was reduced in frequency. Conclusions: Mentors provide career support and professional growth. Newly credentialed athletic trainers should seek out mentors who can support their continued development. The informal relationship appears to be of the greatest importance during the first few months of practice, and then once comfort and self-confidence improves, the frequency of communication is reduced.