Background: Vitamin D, also known as the sunshine vitamin, is formed in the skin from exposure to sunlight, and is absorbed from foods as well. It is important for calcium absorption and bone growth. Vitamin D status is linked to the pathogenesis of skeletal and non-skeletal disorders. Vitamin D deficiency is relatively prevalent all over the world. In studies conducted in other countries, adolescents are thought to have increased risk of vitamin D deficiency. Still, data is lacking about the prevalence of vitamin D deficiency among healthy Afghan adolescents. Objective: The aim of this study was to determine the prevalence of and to identify factors associated with vitamin D deficiency and severe vitamin D deficiency among Afghan adolescents (10-18 years of age) diagnosed at French Medical Institute for Mothers and Children (FMIC), Kabul. Material and Methods: An analytical cross-sectional study design was conducted from Jun to Sep 2016. Blood samples were obtained, serum 25OHD levels were measured, and the patients were divided into five diagnostic categories according to their serum 25OHD concentrations. 1) Sufficiency ≥30-100 ng/ml; 2) Insufficiency ≥20-30 ng/ml; 3) Deficiency <20 ng>/ml; 4) Severe deficiency <10 ng>/ml; 5) Intoxication >150 ng/ml. Collection of samples were made at Clinical Laboratory of FMIC and serum 25OHD analyses were carried out in the Biochemistry section. Results: A total of 308 adolescents were part of the sample for the final analysis. Of all, 202 (65.6%) were females and 106 (34.5%) were males. Out of total, 238 (77.3%) had either insufficiency, deficiency or severe deficiency of vitamin D. Among those, a large number of the participantss i.e., 107 (34.7%) had severe vitamin D deficiency, 81 (26.3%) had vitamin D deficiency, 50 (16.2%) had vitamin D insufficiency, and only 70 (22.7%) had vitamin D sufficiency. There were two cases of vitamin D intoxication, who were excluded from the study. Gender, sun-exposure, usage of sun protector, calcium+vitamin D supplement intake, Vitamin D rich foods intake, regular milk intake, the type of living in yards or apartments, skin colour of participants, and BMI were found as significant factors associated with vitamin D level Conclusion: There was a high prevalence of vitamin D deficiency among adolescents who visited a tertiary healthcare facility in Kabul. Low serum vitamin D concentration is prevalent among general Afghan population. Screening and ongoing investigation for vitamin D deficiency should be considered for all adolescents in the country. Based on our results, the