Type 1 diabetes mellitus (T1DM) is a disease characterised by the autoimmune destruction of insulin-producing pancreatic beta cells. Vitamin D is a known immune system modulator and its effects are exerted via the vitamin D receptor (VDR). Several VDR gene single nucleotide polymorphisms (SNPs) have been commonly studied in relation to T1DM. The aim of this study was to evaluate the role of VDR gene variation in T1DM susceptibility by genotyping four SNPs (FokI-rs10735810, TaqI-rs731236, BsmI-rs1544410, and Tru9I-rs757343) in 160 case-parent trio samples from the population of South Croatia. We observed overtransmission of Tru9I allele G and undertransmission of the Tru9I-BsmI A-A haplotype from parents to affected children (P = 0.032, P = 0.002, respectively). These results indicate a possible role of the VDR gene in T1DM aetiology. In conclusion, this family-based study presents some evidence of association of specific VDR gene variants with T1DM in the population of South Croatia.