BackgroundMelanoma develops in the cells that produce melanin; ocular melanoma accounts for 3–4% of all malignant melanomas. Thyroid tumors are the most common endocrine neoplasms, with more than 95% of cases arising from follicular cell origin. Previous studies have reported associations between malignant melanoma and a wide variety of malignancies.Case presentationWe report a 54-year-old Iranian woman who was diagnosed with ocular melanoma based on a mushroom-shaped filling defect with homogeneous echo pattern arising from the anterior third of the temporal side of the globe detected on ocular sonography during routine ophthalmological examination. She underwent right globe enucleation and implant replacement. During tumor surveillance, fluorodeoxyglucose positron emission tomography/computed tomography scan showed low-grade metabolically active tumoral involvement in the anterolateral aspect of the right lobe of thyroid. The patient subsequently underwent thyroidectomy and submandibular lymphadenectomy. Pathologic report demonstrated micropapillary carcinoma (9 × 8 mm2), tall cell variant without lymphovascular or perineural invasion in the base of lymphocytic thyroiditis.ConclusionThis case illustrates the importance of precise active surveillance in case of papillary carcinoma of thyroid or malignant melanoma to avoid missing other associated pathologies and emphasizes the simultaneous treatment of two tumors.