BACKGROUND : Despite advances in device technology and treatment strategies, infection remains a major cause of adverse events (AEs) in mechanical circulatory support (MCS) patients. To characterize the epidemiology of MCS infection, we examined the type, location, and timing of infection in the International Society for Heart and Lung Transplantation Registry (ISHLT) for Mechanically Assisted Circulatory Support (IMACS) over 3 years, 2013 to 2015. METHODS : Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) definitions were used to categorize AE infections occurring in MCS patients within IMACS. The IMACS infection variables were mapped to ISHLT definitions for infection where feasible. Three categories of MCS infection were defined as ventricular assist device (VAD) specific, VAD related, and non-VAD. RESULTS : There were 10,171 patients enrolled from January 2013 through December 2015. Infection was the most common AE, with 3,788 patients (37%) experiencing ≥ 1 infection, and 6,758 AE infections reported overall. Non-VAD infection was the largest category, 4,501: 34.0% pneumonias, 30.6% non-VAD-related bloodstream infections (BSIs), 24.15% urinary tract infections (UTIs), and 10.2% gastrointestinal infections. VAD-specific infection was the second largest category, 1,756: 82.9% driveline, 12.8% pocket, and 4.3% pump/or cannula infections. VAD-related infection was the smallest category, 501: 47.5% BSIs, 47.5% mediastinitis, and 5.0% mediastinitis/pocket infections. All 3 categories were more frequently reported ≤ 3 months after implant. CONCLUSIONS : Non-VAD infection, including pneumonia, BSI, UTI, and gastrointestinal infection, was the leading category of infection in MCS patients and the most frequently reported ≤ 3 months after implant. These results provide evidence to support resourcing and strengthening infection prevention strategy early after implantation in MCS.