Childhood obesity or being overweight is a growing international issue. This experimental pretest-posttest control group study examined the effects of an individually-based intervention to improve healthy eating specially for weight controland nutritional status among Thai 10–12-year-olds who were overweight. We report a study,based on the Theory of Planned Behavior, that examined the impact of an intervention on: theintention of children to perform eating behaviors for weight control, their eating behaviorsgenerally, andtheir overall nutritional status. Students from two Thai schools were randomized into either an experimental or control group. Participants of each school,who met the inclusion criteria, were drawn independently into the experimental group (68 children)whoreceived an intervention,while the control group (68 children)received the school’s usual healthy-eating educational program. The Demographic Characteristics Questionnaire, Intention to Perform Eating Behaviors for the Weight Control Questionnaire, and Eating Behaviors for Weight Control Questionnairewere used to gather three data sets. Participants completed the questionnaire at baseline, and at weeks 6 and 18after the intervention.Analysisof the data was performed using descriptive statistics, two-way repeated measuresMANOVA, and independent t-tests. The results revealed significantimprovement in the children of experimental group in theirintention to perform eating behaviors for weight control, eating behaviors, and nutritional statusat all periods of measurements than those in the control group.The findings suggest that nurses need to consider increased adoption of individual-based interventions,based on Theory of Planned Behavior, in order to effectivelyintervene in the obesity epidemic in Thailand.