Purpose. To evaluate the effect of glycemic control on response to therapy of diabetic clinically significant macular edema (CSME). Methods. Patients with CSME had their glycosylated hemoglobin (HbA1c) measured at baseline and 6 months. Central foveal thickness (CFT) and best-corrected visual acuity (BCVA) in logMAR were measured at baseline, 3 months, and 6 months. Therapy included laser and intravitreal bevacizumab. HbA1c was graded as G1 <7%, G23 7%-7.9%, G3 8%-8.9%, G4 >9%. Results. Fifty-two eyes were included with mean logMAR BCVA and CFT as follows: baseline 0.75 and 423±106 µm; 3 months 0.47 and 293±69 µm; and 6 months 0.48 and 324±76 µm. Mean HbA1c was 8.13% and 7.43% at baseline and 6 months, respectively. There was no statistically significant difference between baseline and 6 months HbA1c groups and logMAR BCVAs and CFTs at baseline, 3 months, and 6 months. However, there were positive correlations between baseline HbA1c levels and each of baseline logMAR BCVA (p=0.024), baseline CFT (p<0.001), and 6-month logMAR BCVA (p=0.007). Improved HbA1c by 6 months did not show any correlation with logMAR BCVA and CFT at 6 months. Conclusions. Lower HbA1c appeared to be correlated with better visual acuity and lower CFT values at baseline, and also correlated with significantly better vision and nonsignificantly thinner CFT with therapy at 6 months.