Primary trimethylaminuria (fish-odor syndrome) is a rare autosomal recessive inherited metabolic disorder due to decreased metabolism of trimethylamine by enzyme flavin-containing monooxygenase 3. We report an adolescent boy who was socially distressed with malodor and diagnosed trimethylaminuria by molecular analyses. The patient was previously found to have primary hypothyroidism at another center when he was being investigated for malodor. Our aim is to remind awareness of this rare, socially devastating metabolic disorder to physicians, especially family doctors and specialists such as pediatricians, adolescent doctors, psychiatrists and dermatologists. We also searched for a possible association between trimethylaminuria and hypothyroidism but didn`t find out an exact pathophysiological link. Coexistence of primary trimethylaminuria and hypothyroidism might be coincidental. Keywords : trimethylaminuria, fish odor syndrome, malodor, FMO3, hypothyroidism