Pneumonic plague is one of the clinical forms of plague, of low frequency and high mortality, transmitted by direct inhalation of Yersinia pestis coming from an animal or from person to person. Objective. To describe the clinical and epidemiological characteristics of the cases of primary pneumonic plague in an outbreak in the north of Peru. Materials and methods. The clinical records of the confirmed cases of primary pneumonic plague presenting in an outbreak occurring in La Libertad, in July 2010, were reviewed, also the search and contact investigation was performed. Results. The index case was identified, as well as three additional cases, out of these, two were nosocomial infections related to the index case. The initial clinical presentation was characterized by sudden onset of fever, chills, myalgia and chest pain, which in less than 24 hours evolved to hypotension and cyanosis. The initiation of specific treatment varied from 2 to 12 days, and cases with prompt initiation of treatment had a better clinical outcome. The lethality was 50% (2/4). Conclusion. Nosocomial transmission of pneumonic plague in Peru is evidenced, with severe clinical manifestations and high lethality.