Antibiotic resistance is the ability of microbes to resist antibiotic action despite increasing concentration, and plant extracts have shown potential as antibiotic-sensitizing agents that reduce the dosage of antibiotic use. Thus, in this study, ethanolic extract of Andrographis paniculata was screened for antimicrobial property using modified Kirby Bauer disc diffusion assay. The results showed significant growth inhibition (p<0.05) of Pseudomonas sp., exhibited through the formation of zone of inhibition. Subsequently the minimum inhibitory concentration (MIC) for the ethanolic extract of A. paniculata was determined to be 25 mg/mL, which was the minimum extract concentration that significantly inhibited (p<0.05) the growth of Pseudomonas sp. This MIC of A. paniculata was used to determine if it can prevent bacterial cell adhesion. The results showed no significant (p>0.05) inhibition on bacterial cell adhesion, thus suggesting no inhibition on the biofilm formation by Pseudomonas sp. However, the A. paniculata ethanolic extract can destabilize the outer membrane of the Pseudomonas sp. Thus, the overall results suggest that A. paniculata can still be a good candidate as a sensitizing agent for antibiotics due to the strong antimicrobial and membrane destabilizing activities.