<p>Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is a rare genetic disorder characterized by renal magnesium wasting, hypercalciuria, and progressive renal function decline, often culminating in end-stage renal disease (ESRD). This report presents the case of a successful living-donor kidney transplantation from a mother to her 22-year-old son, who was diagnosed with FHHNC. The patient initially exhibited hematuria at age two years, progressing to recurrent nephrolithiasis and hypercalciuria. Genetic analysis at age nine years confirmed FHHNC because of a <i>CLDN-16</i> gene mutation. The <i>CLDN-16</i> gene, which codes for claudin-16, is a crucial protein involved in renal magnesium and calcium reabsorption. While both parents and one sibling were identified as heterozygous carriers of the mutation, only the patient experienced severe symptoms. As his renal function progressively declined, ultimately reaching ESRD, a living-donor transplant was deemed necessary. His mother, with normal renal function and no history of nephrolithiasis, was evaluated as a suitable donor. Post-transplantation, the patient demonstrated rapid improvement in renal function, with magnesium levels stabilizing to baseline without supplementation, indicating effective graft function. This case underscores the complexities of managing FHHNC, particularly regarding kidney transplantation options and outcomes. Given the rarity of FHHNC, this report highlights the critical role of genetic diagnosis, family screening, and timely intervention. Additionally, it contributes to the limited literature on post-transplant outcomes in FHHNC, emphasizing the potential for living-donor transplantation to restore renal function and enhance quality of life in affected patients.</p>