Sirolimus is a well-known, potent immunosuppressant that is widely used in solid-organ transplantation, but it is not without potential side effects. A rare but devastating adverse effect is sirolimus-associated pulmonary toxicity. We report a case of sirolimus-induced diffuse alveolar hemorrhage confirmed by bronchoscopic findings (after other possible etiologies were ruled out) and by clinical and radiographic resolution of the pulmonary signs and symptoms a few days after sirolimus administration was stopped. This case and the existing literature on this topic suggest that sirolimus-induced pulmonary toxicity should be suspected in any patient taking immunosuppressants and who develops unexplained pulmonary symptoms.