Mycoplasma pneumoniae–induced rash and mucositis (MIRM) is a severe and uncommon entity in the pediatric population, characterized by predominant mucosal involvement, limited cutaneous manifestations, and preceding systemic prodromal symptoms. However, infection caused by this pathogen is common in this age group. Its clinical presentation may mimic more frequent conditions, such as herpetic gingivostomatitis in milder cases, or resemble Stevens–Johnson syndrome in more severe presentations. We report the case of an 8-year-old boy presenting with fever and oral and periocular vesicular lesions, initially diagnosed with herpetic gingivostomatitis, who subsequently showed poor clinical evolution. Etiological investigation confirmed Mycoplasma pneumoniae infection. Early recognition of this entity is essential in the Primary Care setting.