To describe presenting symptoms and signs according to age group in a cohort of 243 patients with tuberous sclerosis complex (TSC) and identify earlier symptoms and signs that did not lead to immediate diagnosis. We performed a retrospective chart review for 278 patients with TSC who were examined at Children's Hospital Boston in Massachusetts and at the Herscot Center for Tuberous Sclerosis Complex, Massachusetts General Hospital. The presenting symptom or sign was the first symptom or sign to cause suspicion for TSC and lead to diagnosis. Missed symptoms or signs were those that were documented in the patient's chart but did not immediately lead to diagnosis. There were 243 patients for whom there were sufficient data for inclusion in this study. Patients were diagnosed with TSC at ages ranging from birth to 73 years. The average age at diagnosis was 7.5 years. Of the patients, 81% were diagnosed before the age of 10. Diagnosis during adolescence and adulthood was not uncommon. The most common presenting symptoms and signs included new onset of seizures, history of seizures, infantile spasms, family history of TSC, cardiac rhabdomyomas, and hypopigmented macules. Of the patients, 39% reported missed symptoms or signs of TSC, most commonly seizures (including infantile spasms) and dermatologic features. Many patients had symptoms or signs of TSC that did not lead to immediate diagnosis. Clinicians should be aware of the myriad potential presenting symptoms and signs of TSC. Early diagnosis may reduce morbidity and mortality.