We report the diagnosis of an unsuspected pseudoaneurysm in the lower extremity when 3-phase bone scan was used to evaluate a presumed malignancy. We confirmed the diagnosis with duplex ultrasonography and angiography. Although the primary diagnostic modality for detection of pseudoaneurysm remains duplex sonography, the nuclear medicine practitioner should be vigilant for characteristic presentation of a pseudoaneurysm on a 3-phase bone scan, an area of increased radiotracer activity on blood-flow and blood-pool images that becomes a photopenic area on delayed images. This also underscores the need to consider benign vascular lesions in the differential diagnosis of abnormal 3-phase bone scans for presumed tumors.