OBJECTIVE: To assess the effectiveness of a LINE-based insulin injection support program on knowledge, insulin adherence, and capillary blood glucose levels in patients with uncontrolled type 2 diabetes. METHODS: A quasi-experimental, two-group pretest-posttest study was conducted with 60 patients from a diabetes clinic in a tertiary hospital in southern Thailand, recruited via simple random sampling. The control ( = 30) and the experimental ( = 30) groups were analyzed using descriptive statistics, Chi-square, Fisher's exact, paired t-tests, and independent t-tests. RESULTS: The study found that, after the intervention, the experimental group demonstrated significant improvements in knowledge ( = 4.90,  = 1.47) and insulin adherence behaviors ( = 17.53,  = 1.70) compared to both their baseline and the control group ( < 0.05). In contrast, no significant difference in blood glucose levels was observed between the groups ( = -0.41,  > 0.05). Baseline scores for knowledge, insulin adherence, and blood glucose levels did not differ significantly between the groups ( > 0.05). CONCLUSION: A LINE-based insulin injection support program effectively improves knowledge and insulin adherence in patients with type 2 diabetes. Nurses can use this program to provide education and monitor adherence, promoting sustained behavioral improvements.