The transition of Kenya's pioneer Competency-Based Education (CBE) cohort from Junior Secondary School (JSS) to Senior Secondary School (SSS) requires classrooms, laboratories, learning materials and teachers that many schools in marginalized counties lack. The purpose of this study was to examine how resource adequacy affects transition from junior to senior secondary school in Garissa County, Kenya. The study was anchored on Schlossberg's transition adaptation theory and supported by distributed leadership theory. A qualitative, descriptive phenomenological design was adopted. The target population comprised 82 respondents, namely 57 JSS heads, 21 SSS heads and 4 sub-county education officers in Dadaab, Fafi, Balambala and Garissa Township sub-counties, all of whom were targeted through a census. Data were collected through semi-structured interviews and document analysis; 78 participants took part, a response rate of 95%. Data were analyzed thematically using NVivo 14. Only 35% of participants rated their infrastructure as adequate for the new system, 40% reported sufficient financial and material resources, and 35% reported inadequate teacher deployment. Inadequate funding was the most cited challenge (45%). Overcrowded classrooms, shortages of textbooks and laboratory equipment, and teacher vacancies pushed schools to simplify competency-based activities. The proposition that inadequate resources constrain effective transition was therefore supported. The study concludes that resourcing, rather than planning intent, is the binding constraint on the transition. It recommends needs-weighted capitation, dedicated transition grants, hardship incentives for teachers and formalized inter-school and community resource-sharing arrangements.