Background. It is unknown whether the coexistence of type 1 diabetes (T1D) and celiac disease (CD) increases the risk for vitamin D deficiency. Aims. To determine the vitamin D status and the risk for vitamin D deficiency in prepubertal children with both T1D and CD compared to controls, TID, and CD. Subjects and Methods. Characteristics of 62 prepubertal children of age 2-13 y with either CD + T1D (n = 22, 9.9 ± 3.1 y), CD only (n = 18, 8.9 ± 3.3 y), or T1D only (n = 22, 10.1 ± 2.8 y) were compared to 49 controls of the age of 8.0 ± 2.6 years. Vitamin D deficiency was defined as 25(OH)D < 50 nmol/L, overweight as BMI of >85th but <95th percentile, and obesity as BMI > 95th percentile. Results. The 4 groups had no difference in 25(OH)D (ANOVA P = 0.123) before stratification into normal-weight versus overweight/obese subtypes. Following stratification, 25(OH)D differed significantly between the subgroups (F (3,98) = 10.109, ANOVA P < 0.001). Post-hoc analysis showed a significantly lower 25(OH)D in the overweight/obese CD + T1D compared to the overweight/obese controls (P = 0.039) and the overweight/obese CD (P = 0.003). Subjects with CD + T1D were 3 times more likely to be vitamin D deficient (OR = 3.1 [0.8-11.9], P = 0.098), compared to controls. Conclusions. The coexistence of T1D and CD in overweight/obese prepubertal children may be associated with lower vitamin D concentration.