OBJECTIVE To determine the origin of grouped cases of Pneumocystis pneumonia in solid-organ transplant recipients at our institution. DESIGN A case series with clinical examinations, genotyping, and an epidemiological survey. SETTING A university hospital in France. PATIENTS We report 12 solid-organ transplant recipients with successive cases of Pneumocystis pneumonia that occurred over 3 years; 10 of these cases occurred in a single year. METHODS We used molecular typing of P. jirovecii strains by multilocus sequence typing and clinical epidemiological survey to determine potential dates and places of transmission. RESULTS Between May 2014 and March 2015, 10 solid-organ transplant recipients (5 kidney transplants, 4 heart transplants, and 1 lung transplant) presented with Pneumocystis pneumonia. Molecular genotyping revealed the same P. jirovecii strain in at least 6 patients. This Pneumocystis strain was not identified in control patients (ie, nontransplant patients presenting with pulmonary pneumocystosis) during this period. The epidemiological survey guided by sequencing results provided information on the probable or possible dates and places of contamination for 5 of these patients. The mobile infectious diseases unit played a coordination role in the clinical management (adaptation of the local guidelines) and epidemiological survey. CONCLUSION Our cardiac and kidney transplant units experienced grouped cases of pulmonary pneumocystosis. Genotyping and epidemiological surveying results suggested interhuman contamination, which was quickly eliminated thanks to multidisciplinary coordination. Infect Control Hosp Epidemiol 2017;38:179-185.