Multidrug-resistant (MDR) Pseudomonas aeruginosa infections represent major a public health concern and require comprehensive understanding of their genetic make-up. This study investigated the first occurrence of IMP-carrying MDR P. aeruginosa strains from Bulgaria. Whole genome sequencing identified a novel plasmid-mediated blaIMP-100 allele located in a In1300-like integron embedded in a novel putative transposon. Two other closely related chromosomal blaIMP variants IMP-13 and IMP-84 were also detected. The IMP-producers were resistant to last-line drugs including cefiderocol (CFDC) (2 out of 3) and susceptible to colistin. The blaIMP-13/84 cassettes were situated in a In320 integron inserted in a Tn5051-like transposon as previously reported. Lastly, the p47825-IMP plasmid rendered PAO1 transformant resistant to CFDC, suggesting a transferable CFDC resistance. A variety of virulence factors associated with adhesion, antiphagocytosis, iron uptake, quorum-sensing, as well as secretion systems, toxins, and proteases were confirmed, suggesting significant pathogenic potential consistent with the observed strong biofilm formation. Emergence of IMP-producing MDR P. aeruginosa is alarming as they remain unsusceptible even to last geneneration drugs like CFDC. Newly detected IMP-100 was even located in an CFDC-resistant XDR strain.