In the search for new antimicrobial molecules， antimicrobial peptides (AMPs) offer a viable alternative to conventional antibiotics， as they physically disrupt the bacterial membranes， leading to membrane disruption and eventually cell death. In particular， the group of linear α-helical cationic peptides has attracted increasing research and clinical interest. The AMP P5 has been previously designed as a cationic linear α-helical sequence， being its antimicrobial and hemolytic properties also evaluated. In this work， we analyzed the feasibility of using P5 against a carbapenem-resistant clinical isolate of Pseudomonas aeruginosa， one of the most common and risky pathogens in clinical practice. After antimicrobial activity confirmation in in vitro studies， synergistic activity of P5 with meropenem was evaluated， showing that P5 displayed significant synergistic activity in a time kill curve assay. The ability of P5 to permeabilize the outer membrane of P. aeruginosa can explain the obtained results. Finally， the antibiofilm activity was investigated by viability analysis (MTT assay)， crystal violet and confocal imaging， with P5 displaying mild biofilm inhibition in the range of concentrations tested. Regarding biofilm disruption activity， P5 showed a higher efficacy， interfering with biofilm structure and promoting bacterial cell death. Atomic force microscope images further demonstrated the peptide potential in P. aeruginosa biofilm eradication， confirming the promising application of P5 in multi-resistant infections therapeutics.