Context: WHO estimates that around two billion people are anemic with approximately 50% of all anemia attributable to iron deficiency. Weekly Iron and Folic Acid Supplementation Program is implemented in school, in various countries to reduce prevalence of anemia in adolescents. Aims: To find out baseline prevalence of anemia and its determinants in urban school-going children of Mumbai. Settings and Design: The cross-sectional study was carried out from August to October 2012 on sample size of 385 school children, selected by systematic random sampling of class VI to X of government-aided school. Materials and Methods: After a written-informed consent, students were interviewed by pre-tested, semi-structured questionnaire and then weight and height were recorded. Hemoglobin was estimated by cyanmethemoglobin method using a colorimeter. Data was analyzed by SPSS version 16. Statistical Analysis Used: Proportion, Chi-square test, Co-relation Co-efficient and Unpaired t test. Results: Mean age was 12.9 years with SD of 1.5 years. Overall prevalence of anemia was 53.2% with prevalence in females and males 56.5% and 50%, respectively. Proportion of mild, moderate and severe anemia was 21.6%, 30.9% and 0.8%, respectively. Age was significantly associated and negatively co-related with mean hemoglobin values with highest prevalence in age group of 15 to 19 years. Anemia was significantly associated with attainment of menarche. Practice of eating green leafy vegetables, groundnuts and egg was significantly higher in males as compared to females. Tiredness and palpitation were significantly higher in females as compared to males. Very few students (2.9%) were aware about anemia. Only 75% of the students were willing to consume weekly iron and folic acid supplementation for a year. Conclusions: Both males and females are susceptible to anemia with highest prevalence in age group of 15 to 19 years. Awareness of anemia was very poor in school-going children.