The routine use of (18)F-fluorodeoxyglucose-positron emission tomography (PET)/computed tomography scans for staging and assessment of treatment response for cancer has resulted in a large number of thyroid abnormalities being detected as incidental findings ("incidentalomas"). Since most PET/CT scans are performed in the setting of a known nonthyroid malignancy, the need for "incidentalomas" to be further investigated and managed depends on the stage, prognosis, and current treatment plan for the known malignancy. We present a case describing the management of an incidental F-fluorodeoxyglucose-avid thyroid nodule detected in a patient with known metastatic colorectal cancer. On the basis of this case, we discuss the management of incidental PET-detected thyroid nodules in patients with metastatic cancer. Thyroid "incidentalomas" must be seen in the context of the prognosis and treatment plan for the known malignancy.