A prospective study was conducted at the tenth Siriraj diabetes camp with the objectives of evaluating the effectiveness of diabetes camp on 1) glycemic control, 2) knowledge, 3) quality of life, and 4) self-care behavior of adolescents with type 1 diabetes (T1D) who participated in the diabetes camp. During the 5-day camp, twenty-seven participants (mean age 15.6±2.1 years, mean duration 6.3±3.0 years) were taught diabetes self-management education (DSME) and engaged in psychosocial support sessions. Post-camp activities were held every 3 months and participants were followed for 12 months post-camp. Glycemic control was assessed prior to the camp, then every 3 months. Knowledge level was assessed prior to the camp, at the end of the camp, and every 3 months. Diabetes self-care behavior and quality of life were evaluated prior to the camp, at 3 months and 12 months after the camp. After attending the camp, participants had improve­ment in knowledge but there were no changes in HbA1c levels or quality of life scores. Quality of life was not consistently associated with HbA1c. In general, participants did not perceive their quality of life was poor or feel having diabetes affected their social life. The issue participants worried about most was whether they would develop complications from diabetes. There were several weak points found among participant self-care behavior, particularly in diet-related matters. Despite no improvement in glycemic control, participants gained knowledge from attending the camp. Diet related self-care behavior is difficult for teenagers with T1D to be compliant with.