Obesity is currently viewed as a serious worldwide public health issue. In this survey, we aim to determine its prevalence among schoolchildren and teenagers in Dakar. The sample of our survey consisted of 2,356 students aged 11-17, including 1,110 boys and 1,246 girls. For each of them, we have calculated their body mass index. Based on the higher value of the norm of that index, referred to the 97th percentile of Rolland-Cachera MF's curves, we have identified obese students according to their age and sex. The prevalence of obesity within our sample is 9.34%, with 2.88% for boys and 6.46% for girls. It is at its peak in the age of 11, though there is no significance (p > 0.05) in its decrease (from age 12 to 17). There are significantly (p < 0.05) more obese students in "catholic private" schools than in "public" schools where schooling is free. Child and teenage obesity is a reality in Dakar schools. Consequently, it is advisable to determine its nationwide prevalence to take on its prevention as well as its cure.