Purpose: This study explores the key determinants and their impact on the effectiveness of successful occupational competency assessments in Ethiopia. Design/methodology/approach: The study used a mixed-methods approach with a concurrent embedded design, collecting data from various stakeholders, including candidates, trainers, assessors, supervisors and industry professionals. The study employed purposive sampling, leveraging their extensive experiences. A high Cronbach's alpha confirmed the instrument's reliability. Quantitative data was analyzed using mean, standard deviation, t-test, Pearson's correlation and regression, while qualitative data was evaluated using thematic analysis. Findings: The study highlights the positive aspects of Ethiopian Center of Competency (CoC) institutions, including the safety of assessment tools and ethical behavior by shop assistants. However, obstacles like institutional autonomy, assessor incompetence and one assessor per session impact effectiveness. The study found that factors related to CoC institutions and assessment centers have the biggest impact on how effective competency assessments are, ranking first and second. The study suggests that the Ministry of Labor and Skill should grant regional CoC agencies autonomy to integrate industry and competency assessments. Originality/value: The study investigates occupational competency assessment in Ethiopia, a relatively unexplored area in competency-based education. It addresses Ethiopia's regulatory and institutional challenges, providing practical insights into competency-based education in developing countries. Key determinants like CoC institutions, assessment centers and assessors' competencies are identified, offering policy recommendations for shaping assessment practices across Africa and other regions. Using the Social-Ecological Systems Framework (SESF) in competency assessment processes provides a new way to think about assessments, adding depth to the conversation on how these processes work.