Purpose: To assess the effect of intravitreal injection of bevacizumab on central choroidal thickness (CCT) and its relationship with central macular thickness (CMT) and best-corrected visual acuity (BCVA) changes in eyes with center-involving diabetic macular edema. Methods: This prospective interventional case series included 20 eyes of 20 patients with center-involving diabetic macular edema naive to treatment. The BCVA assessment, complete eye examination, enhanced depth optical coherence tomography, and fluorescein angiography were performed at baseline followed by 3 monthly intravitreal injection of bevacizumab. The treated eyes underwent BCVA evaluation and enhanced depth optical coherence tomography at Months 1, 2, 3, and 6 after the first injection. Change of the CCT was the primary outcome measure. Secondary outcome measures included BCVA and CMT changes and their relationship with CCT changes. Results: Mean age of patients was 63.1 +/- 8.0 (range, 52-75) years. Mean baseline CCT was 265 +/- 79 mu m, which reduced to 251 +/- 81 mu m and 232 +/- 82 mu m at Months 3 and 6, respectively (P < 0.001). Corresponding values for CMT were 470 +/- 107 mu m, 392 +/- 104 mu m, and 324 +/- 122 mu m, respectively (P < 0.001). The BCVA improved from 20/60 at baseline to 20/50 at Month 3 and 20/40 at Month 6 (P = 0.007). Each 1 mu m decrease in CCT was associated with 2.74 mu m reduction in CMT and 0.1 Early Treatment Diabetic Retinopathy Study letter score improvement in BCVA (P < 0.001 and P = 0.001, respectively). Conclusion: After treatment of diabetic macular edema with intravitreal injection of bevacizumab, CCT decreased and this reduction significantly correlated with CMT reduction and vision improvement.