Purpose The aim of this study was to determine the impact of diabetes in patients with and without dry eyes (DE) on central corneal thickness (CCT) measurements. Methods Eighty-six subjects (51 diabetics and 35 controls) participated in the study. Ultrasound pachymetry was used to measure the CCT, whereas tear break-up time (TBUT) and Schirmer tests were conducted for tear assessments. The participants were divided into group 1 (diabetics without DE), group 2 (diabetics with DE), and group 3 (nondiabetics controls). The measurements were compared using analysis of variance. Results The mean (95% confidence interval [CI]) of CCT was 610 (599 to 620), 601 (582 to 618), and 583 (576 to 589) μm, respectively, in diabetics without DE, with DE, and the control groups. There was significant difference in mean CCT between diabetics without DE and controls ( P < 0.0001), but no significant difference in diabetics with DE versus controls ( P > 0.05). The mean (95% CI) values for TBUT and Schirmer tests were 14 (13 to 15), 6 (4 to 6), 14 (14 to 15) seconds, and 21 (19 to 23), 7 (6 to 8), and 20 (19 to 21) mm, respectively, for diabetics without DE, with DE, and the nondiabetic groups. Conclusions DE affects the CCT in diabetic subjects, having a predilection for lower values in those exhibiting DE. In addition, the results also support the view that diabetics tend to present with higher CCT values when compared with nondiabetic patients.