Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18FDG-PET/CT) has been used to diagnose vasculitis, tuberculosis and malignancy. As PET/CT scans show hotspots during an activation of clinically suspected lesions, they are widely used for diagnosis. However, there are rare cases of PET/CT images for vasculitis combined with tuberculosis. Here, we report a case of eosinophilic granulomatosis with polyangiitis in a patient with disseminated non-tuberculous mycobacterial infection in multiple sites mimicking metastatic malignancy and describe the associated PET/CT scan findings before and after treatment.PET/CT can better inform accurate diagnosis for detecting biopsy sites and differentiating diseases.Eosinophilic granulomatosis with polyangiitis and non-tuberculous mycobacterial infection have been diagnosed simultaneously in this case.The therapeutic response can be assessed with PET/CT in patients with eosinophilic granulomatosis with polyangiitis.