At Queen Sirikit National Institute of Child Health, asthma has been the leading chronic disease for hospital admissions for many years. Pharmaceutical care in asthma clinics in the United States has been well developed. However, it is uncertain whether this can be translated into a Thailand model due to differences in the health care system. The aim was to determine whether patient outcomes could be improved by the delivery of pharmaceutical care to pediatric asthma patients. The study design was a prospective randomised controlled trial. The study was carried out at Queen Sirikit National Institute of Child Health. Patients were randomised to either the active (intervention) or the control (usual care) group. Pharmacists identified drug therapy problems (DTPs) and generated a pharmaceutical care plan. Patients returned to see a pharmacist at an interval of approximately 6 months. The number of drug therapy problems (DTPs) was collected. A total of 50 patients were selected to participate in this study, of which 44 (88%) patients completed the study. Of these patients, twenty-two were randomly assigned to the active group. At the initial visit, a total of 24 DTPs were identified from 11 control patients, whereas 21 DTPs were identified from 11 active patients. At follow-up, 29 and 5 DTPs were identified from 16 control and 5 active patients, respectively. In this study a pharmaceutical care model for pediatric asthma patients was developed successfully and evaluated. The result showed that there was a significant decreased in the number of DTPs in the active group compared to the control group. The data suggest that having pharmacists provide pharmaceutical care for pediatric patients with asthma results in a favorable outcome.