Tuberous sclerosis complex (TSC) is a neurocutaneous syndrome and multisystem disorder with autosomal dominant inheritance and variable penetrance. Cardiac rhabdomyomas have been reported in 50–64% of patients with TSC and transthoracic echocardiography is established as the primary imaging modality for their detection. The precise functional assessment of the left ventricle in these patients requires clarification. We report a case of a 19-year-old male with known TSC who was referred for outpatient transthoracic echocardiography (TTE) to investigate for the presence of cardiac rhabdomyomas. TTE demonstrated multiple rhabdomyomas with a normal ejection fraction but altered global and regional deformation on speckle tracking. The regional longitudinal strain was notably reduced in the anterior septum (−11%) and inferior septum (−15%). The global circumferential strain (GCS) was significantly reduced at −15.6%. The distribution of regional circumferential strain reduction for the mid-ventricular segment correlated with the location of cardiac rhabdomyomas.