A cross-sectional comparison study was conducted to determine the prevalence of overweight and obesity among schoolchildren 428 children aged 6 -12 years in Dodoma and Kinondoni municipalities in Tanzania. Anthropometric and body composition measurements were taken for all respondents. A total of 428 children were involved in the study. The prevalence of obesity among children aged 6 - 9 years in Dodoma and Kinondoni were 5.6% (n = 118) and 6.3% (n = 87), respectively. Likewise, 4.2% (n = 118) of children aged 6-9 years in Dodoma were overweight while 8.6% (n = 87) of their counterparts in Kinondoni municipality were overweight. For children aged 10-12 years, 3.9% (n= 118) in Dodoma were obese compared to 5.8% (n = 87) of their peers in Kinondoni. Some 4.9% of the children aged 10-12 years in Dodoma were overweight compared to 5.8% of their counterparts in Kinondoni. The average body fat mass of children aged 6 - 9 years in Dodoma ranged from 21.42-21.81%, while that of their peers in Kinondoni ranged from 21.66-21.98%. The average body fat mass of children aged 10-12 years ranged between 23.95-24.10% in Dodoma and 23.65-24.95% in Kinondoni. There were gender and age differences in body fat mass distribution, with girls and the older children having significantly (P < 0.05) higher proportion of body fat mass. In conclusion, although the prevalence of overweight and obesity among children in this study were lower than those reported elsewhere, there is an imminent danger because the trend of the conditions is rising swiftly with urbanization, changes in lifestyles and socio-economic transition. It is recommended that, children should be educated on good nutrition practices and trained to develop healthy eating behaviours. Parents should encourage lifestyle behaviours that promote high level of physical activities. Physical education and organized sports at schools should be revived.