Anti-TNFalpha therapy is an effective treatment of Crohn's disease. There is an increased risk of infection, including atypical infection associated in infliximab treated patients. We report a case of a young man who developed Pneumocystis jiroveci pneumonia shortly after starting therapy with infliximab. Thus, although rare, prophylaxis against Pneumocystis jiroveci pneumonia might be considered when starting a treatment with infliximab, especially in patients receiving concomitant immunosuppressive agents.