The purpose of this study was to explore and contextualize leadership development practices of secondary school principals in Oromia National Regional State using a parallel mixed research design. Data were collected from 48 principals and four education officials via questionnaires, semi-structured interviews, and document analysis. Quantitative data were analyzed using descriptive statistics and qualitative data through thematic categorization. The findings of the study revealed that the majority (68.8%) of public secondary school principals were assigned to principalship positions without any form of leadership preparation and, hence, were found to be underqualified to lead at this particular level. Exacerbating the problem, a considerable number of them had no appreciable experiences in school principalship. The study further indicated that professional development opportunities were scarce, mostly consisting of self-initiated activities such as unstructured daily experiences and reading guidelines. Education office-led initiatives were also sporadic and unsystematic, focusing on experience sharing, school visits by supervisors, and occasional meetings at the Woreda level. Despite the Federal Ministry of Education's efforts to establish policies for professionalizing educational leadership, there remains a significant gap between policy and practice, implying that these initiatives have not been effectively implemented on the ground.