INTRODUCTION: Germline DICER1 mutations have recently been identified in familial multinodular goitre (MNG). The natural history of thyroid nodules in DICER1 carriers in children is unclear. The purpose of this study was to describe the clinical and genetic findings of childhood-onset MNG with DICER1 carrier in a patient who underwent total thyroidectomy. CASE PRESENTATION: The 6-year-old proband had a thyroid nodule, and the number and size of nodules increased over 3 years. A total thyroidectomy was chosen because of the rapid rise in thyroglobulin levels, discomfort when swallowing, and the mother's history of poorly differentiated thyroid cancer (PDTC). Histopathology revealed adenomatous goitre without malignant cells. Her mother, maternal aunt, and maternal grandmother also had thyroid nodules removed during adolescence. Also, her mother had PDTC with lung metastases, and her maternal aunt had an ovarian germ cell tumour. DICER1 mutation analysis identified a heterozygous novel nonsense mutation (c.4509C>G, p.Y1503X) for the patient, her mother, her maternal grandmother, and her asymptomatic elder brother. Y1503X was identified in all resected thyroid tissues, while heterozygous D1709G, D1810V, and E1813K mutations were identified in individual nodules. DISCUSSION/CONCLUSION: A thyroid nodule was detected in chemotherapy- or radiotherapy-naïve patient with DICER1 carrier aged 6 years, and MNG developed over 3 years. This pedigree highlights the natural history of nodular disease in DICER1 carriers and identifies a possible association between DICER1 and more aggressive malignancies.