Li-Fraumeni syndrome (LFS) is a rare familial disorder caused by germline TP53 mutations. Despite the establishment of the revised Chompret criteria to guide genetic testing for TP53, identifying LFS in patients who do not satisfy these criteria remains a challenge. Herein, we present the case of a 50-year-old woman with a history of breast, lung, colorectal, and tongue cancers who did not satisfy the revised Chompret criteria. However, genetic testing ultimately revealed a TP53 mutation, leading to the diagnosis of LFS. Although her family history did not satisfy the classic LFS criteria, she had a TP53 core tumor before the age of 46 years. This case highlights the importance of considering LFS in patients with a history of multiple cancers and suggests that genetic testing should be considered even in patients who do not satisfy the revised Chompret criteria.