This quasi-experimental study aimed to evaluate a family-based asthma self-management program, based on the individual and family self-management theory and the McMaster model of family functioning. Children aged 7 to 12 with uncontrolled asthma and their families were recruited from an outpatient pulmonary department of a university hospital in Thailand. Thirty-seven child-parent pairs were randomly assigned to three sessions for a period of two months of the family-based asthma self-management program, while 37 child-parent pairs were assigned to the control group. Data were collected at baseline and after implementation at two months by using the Childhood Asthma Control Questionnaire and the Pediatric Asthma Quality of Life Questionnaire, and the measurement of pulmonary function was performed using peak flow meters. Multivariate analysis of covariance (MANCOVA) was employed to analyze the mean difference between the experimental and control groups. The results indicated significant increased asthma control status, pulmonary function, and quality of life in the children from baseline to after implementation in the experimental group that participated in the family-based asthma self-management program. Significant improvement in these three asthma health outcomes was also seen in the experimental group when compared to the control group. It was seen that the family-based asthma self-management program is useful for promoting the self-management of school-age children, enabling the control of symptoms, and enhancing health outcomes regarding asthma.