Continuous monitoring of the body condition of an overweight pediatric patient is of utmost importance for the success of his or her treatment. However, this represents a challenge after the first consultation because many parents present problems of time to attend the controls in the office, in addition to lack of tools to support monitoring from home, thus causing a high rate of dropout. There are telemonitoring applications for people with obesity that send data in real time, but they are focused on adults; they do not consider pediatric patients or their parents as agents of change. For this reason, TCO is presented as a mobile application for telemonitoring and control of overweight and obesity in pediatric patients, which facilitates the specialist in the communication, follow-up, and orientation of their patients through family members or caregivers, considering anthropometric indicators, automatic monitoring through rules, prescription of the food plan, and recommendation of foods and dishes of the season and region. A case study was carried out with two groups of 16 overweight and obese pediatric patients, one of them using TCO. The results show that the dropout rate was reduced by 38%, and both body mass index and average waist circumference improved by 4% and 3%, respectively. In addition, family members who did not dropout were surveyed, and satisfaction was obtained between “High” and “Very High” in the use of the application as an aid to monitoring and compliance with treatment.