Mycotic aneurysms and pseudoaneurysms, though rare, present significant diagnostic and therapeutic challenges. The case follows a 74-year-old male with a history of bladder cancer who developed multifocal mycotic aneurysms and pseudoaneurysms following sepsis. Initially misdiagnosed as a Pancoast tumor, imaging revealed an extensive disease involving the right subclavian artery, proximal descending thoracic aorta, infrarenal abdominal aorta, and right common iliac artery. This case highlights the importance of considering mycotic aneurysms in the differential diagnosis of patients with a history of infection and highlights the role of Computed Tomography Angiography in early diagnosis.