A 65-year-old man was found to have suspected isolated cardiac sarcoidosis on a positron emission tomography (PET) scan to investigate the cause of sustained monomorphic tachycardia. The patient had episodes of palpitations 12 months prior to this admission, but no cause was ever discovered. Cardiac magnetic resonance (CMR) imaging revealed severe hypokinesis of the inferior segments of the left ventricle, which prompted a subsequent 18F-fluorodeoxyglucose (18F-FDG) PET/CT. The findings were consistent with potential isolated cardiac sarcoidosis as a cause of the fibrosis seen in the left ventricle. As such, the patient was commenced on immunosuppressive therapy and remains well to this day after being fitted with an implantable cardioverter defibrillator (ICD). Isolated cardiac sarcoidosis is a rare phenomenon but remains a diagnostic and therapeutic challenge for clinicians. We report a case of how isolated cardiac sarcoidosis can present as a cause of ventricular tachycardia.