Background: Acinetobacter baumannii infections cause high morbidity and mortality in intensive care unit (ICU) patients. However, there are limited data on the changes of longterm epidemiology of imipenem resistance in A. baumannii bacteremia among pediatric ICU (PICU) patients. Methods: A retrospective review was performed on patients with A. baumannii bacteremia in PICU of a tertiary teaching hospital from 2000 to 2016. Antimicrobial susceptibility tests, multilocus sequence typing (MLST), and polymerase chain reaction for antimicrobial resistance genes were performed for available isolates. Results: A. baumannii bacteremia occurred in 27 patients; imipenem-sensitive A. baumannii (ISAB, n = 10, 37%) and imipenem-resistant A. baumannii (IRAB, n = 17, 63%). There was a clear shift in the antibiogram of A. baumannii during the study period. From 2000 to 2003, all isolates were ISAB (n = 6). From 2005 to 2008, both IRAB (n = 5) and ISAB (n = 4) were isolated. However, from 2009, all isolates were IRAB (n = 12). Ten isolates were available for additional test and confirmed as IRAB. MLST analysis showed that among 10 isolates, sequence type 138 was predominant (n = 7). All 10 isolates were positive for OXA-23-like and OXA-51-like carbapenemase. Of 27 bacteremia patients, 11 were male (41%), the median age at bacteremia onset was 5.2 years (range, 0–18.6 years). In 33% (9/27) of patients, A. baumannii was isolated from tracheal aspirate prior to development of bacteremia (median, 8 days; range, 5–124 days). The overall case-fatality rate was 63% (17/27) within 28 days. There was no statistical difference in the case fatality rate between ISAB and IRAB groups (50% vs. 71%; P = 0.422). Conclusion IRAB bacteremia causes serious threat in patients in PICU. Proactive infection control measures and antimicrobial stewardship are crucial for managing IRAB infection in PICU.