Mefloquine is indicated as oral treatment and as prophylaxis for malaria in areas where chloroquine-resistant malaria is present. Gastrointestinal and neuropsychiatric side effects of mefloquine are well known. More severe neuropsychiatric disorders such as psychosis, depression, hallucinations, and seizures are also reported in the literature. We are reporting a case of drug-induced pneumonia due to mefloquine. This diagnosis was confirmed 4 months after the adverse event, after restarting the same malaria prophylaxis, which could be considered as an unintentional provocation test. This is the third case report in the literature of acute lung injury caused by mefloquine.