Aim/Purpose: In this case study research, we aimed to understand the development of effective doctoral supervision practices in Educational Research by examining supervisors’ experiences as doctoral students and how they learned their evolving supervision and mentoring roles as professors. Background: Doctoral supervision is shaped by institutional systems, program structures, research cultures, and national guidelines. Supervisors impact doctoral students’ research experiences, academic success, and personal growth. Many new professors lack formal training, rely on their own experiences being supervised, and learn how to supervise effectively through trial and error and on the job. Methodology: Our case study research involved interviewing five tenured, mid-career doctoral supervisors who were deemed effective based on doctoral student completions. Using reflexive thematic analysis and evaluative coding of interview transcripts, we identified two key findings and nine themes to describe supervisors’ experiences as doctoral students and their on-the-job development and practices as supervisors. Contribution: This study highlights how experiences being supervised as a doctoral student impact and influence the development of supervision practices in combination with various experiences of learning on-the-job during one’s academic career. We expand understanding of the complexity of supervision practice and uncover differences between contemporary contexts and past experiences being supervised. We demonstrate how several supervisors translated impoverished experiences with their own supervisor into targeted efforts to learn how to effectively supervise their own students, to change history, and to deliberately not supervise the way they were supervised. Findings: Two findings are presented: (1) experiences being supervised influence early supervision practices, and (2) learning to supervise on-the-job happens in a variety of ways. Nine themes describe how supervisors’ experiences being supervised influenced their supervisory practices and the various informal on-the-job development approaches, such as learning from students, colleagues, and prior career experiences. Findings highlight the roles of doctoral supervisors, academic peers, doctoral students, programs, and institutions that contribute to developing effective supervisory practices. In our case study, we demonstrate how supervisors can transform academic and research cultures over time. Recommendations for Practitioners: Institutions, programs, and supervisors play crucial roles in ensuring doctoral student success. Institutions should offer structured professional learning and peer mentoring that supports supervisors in developing effective practices early in their careers. By leveraging study findings, institutions can design professional learning opportunities that increase faculty adoption of effective supervision practices and accelerate their learning. Recommendation for Researchers: Given the vital role played by supervisors in research training and talent development of the next generation of researchers and leaders across society, we argue it is crucial to understand and optimize the ways in which doctoral supervisors develop effective supervisory practice as a matter of ongoing research interest. Future research can investigate the importance of intergenerational learning and knowledge transfer in academia, encouraging a more reflective and informed approach to supervisory development. Impact on Society: Findings can inform how to maximize individual, institutional, and governmental investments in higher education. This research can improve outcomes in doctoral education by expanding effective, research-informed development of supervisory practices. Quality supervision impacts doctoral students’ academic success, mental health, and career progression. Understanding supervisory lineage enables universities to enhance current and future doctoral experiences. Future Research: Four questions are provided to guide and promote supervisory development and ongoing research. There is an ongoing need to examine how supervisors and doctoral students define the impact and outcomes of successful supervision and mentoring practices beyond the completion of the thesis.