Gianotti-Crosti syndrome (GCS) is a self-limited condition, mainly affecting children younger than 6 years, less common in adolescents and adults. It consists of a viral exanthema with papular lesions with a flat top and symmetrical distribution, affecting predominantly extremities, gluteal region and extensor surfaces. It is often associated with viral infections but can also be related to bacterial infections, vaccination or be idiopathic. In this report, we present a case of GCS in a 13-year-old healthy female adolescent who presented with fever, odynophagia, prostration and diffuse maculopapular rash. The diagnosis of infectious mononucleosis due to infection by the Epstein-Barr virus was established. On the second week of the disease, a clinical recrudescence occurred, with worsening of the fever and modification of the exanthema characteristics. GCS is often an underdiagnosed entity. The differential diagnosis of viral exanthema can prove to be challenging and clinical suspicion is essential to achieve the diagnosis.