OBJECTIVES: The objective of this study was to evaluate the subfoveal choroidal thickness (SFCT) and choroidal vascularity index (CVI) in children with newly diagnosed type 1 diabetes mellitus (T1DM). METHODS: A total of 80 children (40 with T1DM and 40 healthy controls) were included in this cross-sectional study. Enhanced depth imaging optical coherence tomography (EDI-OCT) images of all participants were analyzed. The SFCT, total choroidal area (TCA), luminal area (LA), stromal area (SA), and CVI measurements were obtained from EDI-OCT images and compared between groups. The effects of HbA1c, fasting plasma glucose, and axial length measurements on choroidal measurements were investigated. Results: There was no significant difference between the groups according to TCA (0.84 [0.57–1.26] vs. 0.88 [0.65–1.16] mm2, p=0.745), LA (0.55 [0.41–0.79] vs. 0.59 [0.43–0.74] mm2, p=0.745), SA (0.27 [0.15–0.47] vs. 0.28 [0.15–0.47] mm2, p=0.935), and CVI (68.03 [66.5–70.5] vs. 67.75 [66.2–69.5] %, p=0.794), respectively. However, T1DM patients had thinner SFCT compared to control subjects (309.0 [327–489] and 398.5 [219–491], p<0.044). No correlation was found between HbA1c, fasting plasma glucose, axial length measurements, and SFCT, TCA, LA, SA, or CVI. DISCUSSION AND CONCLUSION: Children with newly diagnosed T1DM have thinner SCFT in comparison to healthy children, however, no significant difference in CVI was observed between the groups. Long-term follow-up should be used to confirm the impact of the DM duration on CVI.