This case report describes a 19-month-old boy presenting with macropenis, increased stature, and deep voice, who was diagnosed with concurrent choroid plexus carcinoma in the right lateral ventricle and left adrenocortical carcinoma. Subsequent germline testing revealed pathogenic TP53 mutations, confirming a diagnosis of Li-Fraumeni syndrome. Li-Fraumeni syndrome with primary manifestations of macropenis and accelerated linear growth has rarely been documented in the medical literature. This case highlights the critical importance of implementing whole-body imaging modalities in pediatric patients with growth-developmental abnormalities, particularly those suggestive of Li-Fraumeni syndrome, to guide therapeutic decision-making and follow-up monitoring.