<p><i>Klebsiella pneumoniae complex</i> (<i>KPc</i>) is a group of opportunistic pathogens that pose a serious threat to public health. Multidrug resistance is increasing, and limiting therapeutic options. Aztreonam-avibactam (AZA) is a combination of an established β-lactam with a new β-lactamase inhibitor. The aim of this study was to assess the susceptibility of multidrug-resistant <i>KPc</i> strains to AZA. The study included 52 ESβL-positive strains and 152 carbapenemase-positive <i>KPc</i> strains. The susceptibility to AZA was tested using the gradient strip method. AZA showed high activity against <i>KPc</i>, with MICs ranging from 0.032 to 0.75 μg ml^-1 for ESβL-positive strains and from 0.016 to 2 μg ml^-1 for carbapenemase-positive strains. The lowest MIC₅₀ of AZA was obtained for VIM- and ESβL-positive strains at 0.094 μg ml^-1, and MIC₉₀ for ESβL-positive strains was 0.125 μg ml^-1. AZA demonstrated excellent in vitro activity against the analysed strains, suggesting that this antibiotic may be an effective therapeutic option for treating infections caused by multidrug-resistant <i>KPc</i> strains.</p>