We report CT, MRI, and initial and follow-up 18F-fluorodeoxyglucose positron emission tomography/CT (18F-FDG PET/CT) features of a case of primary mucosal melanoma of the lacrimal drainage apparatus in a 76-year-old man. The lesion was identified as an enhancing mass of the right lacrimal sac with extension into the inferior meatus through the nasolacrimal duct on CT. It was hyperintense and hypointense compared with gray matter on T1- and T2-weighted images, respectively, and intensely enhanced on gadolinium-enhanced T1-weighted images. Initial 18F-FDG PET/CT demonstrated mild fluorodeoxyglucose uptake of the mass. Surgical biopsy confirmed the diagnosis. Periodic follow-up 18F-FDG PET/CT demonstrated recurrent disease 18 months after surgery and its progression thereafter. In primary mucosal melanoma of the lacrimal drainage apparatus, CT, MRI, and initial and follow-up 18F-FDG PET/CT may be useful for early detection of the lesion and associated bony changes, lesion characterization, initial staging, and surveillance of recurrent and metastatic diseases, respectively.