Possessing sufficient nutritional knowledge is a necessary component in the prevention and treatment of obesity. A solid understanding of nutrition can help people make appropriate food selections and can also help correct irrational ideas or myths people may believe about food. It is a challenge to provide this information to children in ways that are exciting. Thus, we propose an online video game platform to deliver the information. The objective of this study was to study the efficacy and acceptability of an online game called 'ETIOBE Mates' that was designed to improve children's nutritional knowledge; furthermore, we compare it with the traditional paper-pencil mode of information delivery. A sample of 228 children participated in the study. Participants were divided into two groups: an experimental group (who used ETIOBE Mates) and a control group (who were given a pamphlet). Both groups increased their scores for nutritional knowledge. The interaction between group × time was also statistically significant; it indicated that acquisition of nutritional knowledge was superior in the experimental group. The children considered the serious games platform to be a useful medium for improving their nutritional knowledge. Online games can be an effective method of delivery for preventive and treatment tasks that are otherwise tedious for children.