BACKGROUND: Acinetobacter spp. is an opportunistic pathogen that has demonstrated increasing relevance in nosocomial infections. Carbapenem-resistant strains have been reported worldwide. ----- METHODS: Since 2014, screening for metallo-β-lactamases (MBLs) in all Acinetobacter spp. isolates using phenotypic methods and PCR has been implemented at the University Hospital Center Zagreb. ----- RESULTS: The bacterial strain was isolated from the drain of a child hospitalized in a paediatric intensive care unit and identified as Acinetobacter guillouiae using a MALDI TOF automated system. The strain was resistant to meropenem, ceftazidime, cefotaxime, ceftriaxone, cefepime, sulbactam/ampicillin, gentamicin and ciprofloxacin, intermediately susceptible to piperacillin/tazobactam and imipenem, and susceptible to amikacin and colistin. The Hodge test and combined disk test with EDTA were positive. The MICs of meropenem and imipenem were not reduced by cloxacillin, but a small reduction of two dilutions was observed following the addition of sodium chloride, which indicated that OXA-58 was produced. PCR and sequencing of chromosomal DNA from boiled colonies revealed blaOXA-58 and blaNDM-1 genes. ----- CONCLUSION: This is the first report of NDM-1 in Acinetobacter spp. in Croatia. The early detection of these genes will aid in the prevention and in the achievement of adequate infection control by limiting the spread of these organisms.