Purpose. We assessed the anthropometric and iron status of adolescents from selected secondary schools in Ogun State, Nigeria. Methods. In this cross-sectional study, anthropometric data, nutrient data, and blood samples were collected from 127 adolescents in Nigeria. Demographic information of the adolescents was obtained in the language of choice using validated questionnaires. Anthropometric indices (weight and height), multiple iron status indicator (hemoglobin, serum ferritin, and transferrin receptor) and inflammation marker (C-reactive protein) were measured using standard procedures. Subjects were classified by body mass index (BMI) categories as underweight, normal weight, at risk of overweight, and overweight according to the World Health Organization standard. Results. The mean age of the subjects was 16.0 ± 2.3 years. Majority of the subjects (55.1%) had normal BMI values, 21.3% were underweight, and 14.2% were overweight. Boys had significantly (<0.05) higher mean intake for energy and most nutrients than girls. The dietary iron intake of the adolescents was unsatisfactory, with approximately 80% of the subjects failing to meet RNI level. Using multiple criteria of iron indicators, the prevalence of iron depletion and iron deficiency in the adolescents were 7.9% and 15.0%, respectively. The prevalence of anemia was high (24.4%), with iron deficiency anemia being the most (71%) prevalent. In both boys and girls, ferritin correlated positively with BMI, waist circumference, and waist–hip ratio. Conclusions. This study documented a high prevalence of iron deficiency and poor nutritional status among Nigeria adolescents, which can be used as basic for dietary support and nutritional education to improve their iron status.