Context: Clinical reasoning is an inferential process of collecting and evaluating data in patient cases, necessary in all care. Athletic training residency programs are emerging rapidly as the industry standard for developing clinical specialists who possess advanced clinical reasoning needed for complex cases. Objective: The purpose of this study was to explore current practices of advanced clinical reasoning development and assessment in athletic training residency programs. Design: Inductive qualitative research. Setting: Web-based teleconferencing platform (Zoom Video Communications). Patients or Other Participants: Seven of 10 Commission on Accreditation of Athletic Training Education--accredited residency program directors (RPDs) (age = 46 ± 9 years, years as RPD = 5 ± 6). Data Collection and Analysis: We used qualitative, semistructured interviews. Audio files were transcribed verbatim, checked for accuracy, deidentified, and member checked before analysis. We used a 2-person data analysis team and an inductive coding approach. The researchers reviewed the transcripts independently, met to develop a codebook, applied the codes, and conducted internal auditing. Trustworthiness was established through member checking, multiple-analyst coding, and auditing. Results: Three themes emerged from the RPDs about developing advanced clinical reasoning: (1) defining clinical reasoning; (2) instructional tactics; and (3) assessment tactics. RPDs defined clinical reasoning as the process of the resident justifying their decision-making and the accuracy of their decisions. RPDs described both clinical and didactic instructional tactics, including mentoring, lectures and discussions, case presentations, and journal club. RPDs described assessing advanced clinical reasoning through patient and preceptor feedback in structured and unstructured formats, self-reflection, and knowledge testing to measure clinical reasoning. RPDs highly relied on preceptors and clinical mentoring, but also described a singular reliance on residents to appraise the clinical reasoning capacity of their own preceptors. Conclusions: RPDs define clinical reasoning as rationalization and accuracy of decisions. Although the programs are engaged in effective clinical and didactic approaches to teach advanced clinical reasoning, they rely heavily on the subjectivity of preceptors and residents to assess these outcomes.