<b><i>Background:</i></b> The <i>DEFB1</i> gene, encoding for the constitutively expressed human β-defensin 1 (hBD1) antimicrobial peptide is a potential candidate when studying genetic susceptibility to caries. <i>DEFB1</i> genetic variations have been reported as contributing to hBD1 production impairment, leading to a greater susceptibility to be infected by oral pathogens, also leading to periodontitis. <b><i>Methods:</i></b> We analysed 5 <i>DEFB1</i> polymorphisms, namely 3 functional single-nucleotide polymorphisms (SNPs) at the 5′-untranslated region (UTR), -52G>A (rs1799946), -44C>G (rs1800972), and -20G>A (rs11362), 2 SNPs at the 3′-UTR, c*5G>A (rs1047031) and c*87A>G (rs1800971) SNP located in potential miRNA binding sites, looking for possible correlations with the risk to develop caries in 654 adult subjects from isolated populations of north-eastern Italy. Dental caries prevalence was evaluated with the DMFT (decayed, missing, filled teeth) index, calculated after an accurate oral examination. <i>DEFB1</i> SNP genotyping was performed with an Illumina 370k high-density SNP array. <b><i>Results:</i></b> Two <i>DEFB1</i> SNPs were significantly associated with the DMFT index: the strongest association emerged from rs11362 SNP (<i>p</i> = 0.008). In particular G/G homozygous individuals showed a higher DMFT index compared to both G/A heterozygous and A/A homozygous individuals; rs1799946 SNP was also significantly associated with DMFT (<i>p</i> = 0.030), and individuals homozygous for the T allele had a higher DMFT value compared to heterozygous C/T and homozygous C/C individuals. <b><i>Conclusions:</i></b> Our study replicated, on a larger number of individuals, previous findings showing the association between two 5′-UTR SNPs in the <i>DEFB1</i> gene and DMFT, suggesting that these polymorphisms could be considered as potential markers for assessing the risk to develop caries.