Introduction: The Ministry of Health Malaysia introduced the national best practices for adolescent-friendly health services in 2018 and it served as an assessment tool in the accreditation of adolescent-friendly clinic status. This study was conducted in Kelantan with the objective to determine the proportion of adolescent-friendly clinics and its determinants and perceptions of healthcare providers regarding the facilitating factors in providing adoles-cent-friendly health services. Methods: The research design was sequential explanatory mixed method. State wide clinics assessment was done to estimate the proportion of adolescent-friendly clinics and to determine the factors associated with adolescent-friendly health services provision. Perceptions of healthcare providers on the facilitating factors for adolescent-friendly health services were explored through in-depth interviews. Descriptive statistics and linear regression analysis were performed for quantitative data, and thematic analysis for qualitative data. Results: Out of 85 health clinics, 30 (35.3%) clinics were accredited as adolescent-friendly. Availability of trained health-care providers in adolescent health modules, private room for adolescent counselling, dedicated team in charge of adolescent programme and adolescent health promotional activities were the statistically significant determinants for adolescent-friendly health services (p