Objectives: In recent years, increasing rates of antibiotic resistant infectious pathogens together with the decline of novel antibiotics urged the need to discover powerful antimicrobial therapy. This is aimed to characterize A. columnaris chemically and investigate its antioxidant and antimicrobial activities. Methods: DPPH, ABTS, iron metal chelation, FRAP and ORAC assays were used to evaluate the antioxidant activity. Agar well diffusion and tube dilution methods were employed to detect the antimicrobial activity and the minimum inhibitory concentrations of the plant extracts. Results: A. columnaris exhibit antibacterial activity against Gram-positive pathogens, S. aureus, S. pyogenes and Methicillin Resistant Staphylococcus aureus (MRSA). As for both MRSA and S. pyogenes clinical isolates, the MIC of extract obtained corresponded to concentration 10.4 mg/ml. Moreover, total phenolic and flavonoid contents of aerial parts extract were 39.0161± 1.53 mg GAE and 49.2214 ± 3.47 mg RE per gram of dried extract, respectively. GC/MS analysis of the essential oil of A. columnaris resulted in the detection of eighty-one components (98.03%) with hibaene (23.35%) as a major constituent. Additionally, in-silico study was performed on the identified polyphenolic compounds of A. columnaris against both the PBP2a allosteric site and active site to explain the mechanism of action against MRSA. Conclusion: A. columnaris extract is a potential candidate of an alternative therapy to both infectious and non-infectious diseases and further studies are required to expand the use of A. columnaris as antibacterial for treating resistant Gram-positive pathogens circulating in hospital settings.