The recent exponential surge in vitamin D research reflects the global epidemic of vitamin D deficiency and its potential impact on several chronic diseases in both children and adults. Several subpopulations, including Arab adolescent boys and girls, remain understudied. This study aims to fill this gap. A total of 2225 apparently healthy Saudi adolescents (1187 boys and 1038 girls, aged 13-17 years old) and 830 adults (368 men and 462 women, aged 18-50 years old) were respectively recruited from different public schools and medical practices within Riyadh, Saudi Arabia. Anthropometrics were taken and fasting blood samples withdrawn to examine serum glucose and lipid profile by routine analysis and 25-hydroxyvitamin D by ELISA. Almost half of the girls (47.0%) had vitamin D deficiency as compared to only 19.4% of the boys (p<0.001), 36.8% of the adult women and 17.7% of the adult men (p<0.001). Furthermore, in boys there were more significant inverse associations between serum 25(OH)vitamin D levels and cardiometabolic indices than girls, while in contrast women had more significant associations than men. Vitamin D deficiency was significantly associated with diabetes mellitus type 2 (DMT2) [OR 3.47 (CI1.26-5.55); p<0.05] and pre-DM [OR 2.47 (CI 1.48-4.12); p<0.01] in boys. Furthermore, vitamin D insufficiency was significantly associated with abdominal obesity in boys [OR 2.75 (CI 1.1-7.1); p<0.05]. These associations for DMT2 and abdominal obesity were not observed in adult males, girls and adult women. Vitamin D deficiency/insufficiency and hyperglycemia is high among Arab adolescents. Vitamin D deficiency is mostly associated with cardiometabolic risk factors in adolescent Arab boys. This indicates a sex- and age-related disadvantage for boys with low vitamin D status and challenges the extra-skeletal protection of vitamin D correction in adolescent females.