Objectives: The aim of this study was to assess changes in central macular thickness following uncomplicated phacoemulsification surgery in diabetic patients with and without retinopathy and in a control group. Methods: The records of 43 eyes of patients with mild non-proliferative diabetic retinopathy (NPDR), 43 eyes of diabetic patients without diabetic retinopathy (no-DR), and 43 eyes of a control group that also underwent phacoemulsification surgery were prospectively reviewed. Foveal thickness was measured using optical coherence tomography preoperatively and at 1 week and 1, 3, 6, and 12 months postoperatively. Results: No clinically significant differences in foveal thickness were observed preoperatively between groups. Foveal thickness had increased in the NPDR group at 1 week and 1 and 3 months after surgery, in the no-DR group at 1 week and 1 month, and in the control group at 1 week after surgery. Foveal thickness decreased gradually in the NPDR group after 3 months. When comparing the groups, foveal thickness was significantly greater in the NPDR group than in the no-DR group and the control group at postoperative months 1 and 3; however, at month 6, the differences had decreased, and there were no clinically significant differences between groups. Conclusion: Foveal thickness increased until 3 months after cataract surgery and decreased gradually thereafter in NPDR patients. Foveal thickness had also increased during the first month in the no-DR group. Foveal thickness increased only in the first week in the control group. These changes were more prominent in eyes with NPDR than in eyes with no-DR and those of the control group.