<i>Background:</i> Gitelman’s syndrome (GS) is caused by mutations in the SLC12A3. Most of the mutations are rare, making it difficult to establish a genotype-phenotype correlation. Although GS is a recessive disorder, some patients also have an affected parent, suggesting a dominant inheritance. <i>Methods:</i> We sequenced the 26 coding exons of SLC12A3 in a family in which the proband and her father had a late onset GS. We obtained cDNA of the 2 patients and analyzed the effect of a mutation on pre-mRNA splicing. <i>Results:</i> The 2 patients were homozygous for a nucleotide change in the last nucleotide of exon 15: c.1925 G>A. The mother was a heterozygous carrier for this putative mutation. Amplification of cDNA with primers for exons 14–17 was negative, suggesting that this mutation affected the splicing and promoted mRNA degradation through nonsense-mediated decay. <i>Conclusions:</i> We report a family with 2 patients with late onset GS and homozygous for a mutation in the last nucleotide of exon 15. Our study shows that homozygosity for this mutation resulted in a significant loss of normal SLC12A3 transcript.