This cross-sectional study is aimed to measure the prevalence of patient adherence to treatment regimens and factors affecting glycemic control among Type 2 diabetes patients. 243 diabetes patients seeking care at a tertiary hospital diabetic clinic in Bangkok were interviewed. HbA1c was used as an index of glycemic control. The proportions of cases with good adherence to physical exercise and diet regimen were 31.7 and 54.3%, respectively. About 46.5% reported receiving good social support for diabetes from his/her family. The median of HbA1c was 8% (normal range 4.7-6.3%). Approximately 33.3% achieved good glycemic control (HbAlc < or =7%), while 50.2% had poor control (HbAlc >8%). Multiple logistic regression analysis indicated two variables were significantly associated with glycemic control: adherence to diet control and exercise. Interactive health education should be introduced to increase patient adherence to treatment regimens. Family members should be informed about their important roles in encouraging patients' glycemic control.