BACKGROUND Transfusion of blood products is an essential component of the hematopoietic cell transplantation (HCT) process. Blood transfusion carries several risks including, but not limited to, lung injury. The effect of transfusions on lung complications after HCT has not been previously investigated. STUDY DESIGN AND METHODS We retrospectively studied 215 adult allogeneic HCT recipients at the University of Minnesota and examined the association between transfusion of blood components and development of lung complications after HCT. Patients without lung complications were used as the control group. RESULTS A total of 113 (58%) of the patients developed lung injury events before Day 180 after HCT. Six-month survival was significantly lower in the lung event group (52%) versus the controls (78%; p = 0.01). Patients who eventually developed lung events received more transfusion episodes per week in the first month after HCT (median, 4.3 vs. 2.7 for controls), platelet units per week (3.5 vs. 2.0), and RBC units per week (1.8 vs. 1.4; p < 0.01) for all. In a multivariable analysis, each additional transfusion before Day +30 was associated with a 2.7% higher risk of lung complication (95% confidence interval, 0.8-4.8; p = 0.01), adjusting for time to engraftment, conditioning intensity, and donor type. Blood utilization increased after the lung event and remained high for several months relative to controls. CONCLUSION Our data suggest that transfusion of blood products is associated with and may further complicate lung complications after HCT. Cautious use of blood components in the post HCT period is recommended.