Methicillin-resistance in Staphylococcus aureus is frequently associated with enhanced biofilm formation and the presence of biofilm-associated genes that contribute to treatment failure and persistence. This study characterized the phenotypic biofilm formation and genotypic profiles of 10 clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates and evaluated the dose-dependent antibiofilm activity of the ethanolic extract of oregano (Plectranthus amboinicus). All isolates carried mecA, confirming methicillin resistance in all isolates. The biofilm-associated genes icaA, icaD, and sarA were detected, whereas bap was absent. Despite the absence of bap, all isolates exhibited moderate to strong biofilm formation, consistent with ica-dependent polysaccharide-mediated adhesion. Based on PCR-based detection of the agrII gene (presence/absence), the isolates were classified into agrII-positive (n = 5) and agrII-negative (n = 5) groups. Biofilm formation was predominantly moderate (0.140 < OD < 0.280), with two isolates showing strong biofilm formation (OD > 0.280). Extract dilutions (100%-3.125% v/v) were tested using a modified crystal violet assay. The agrII-positive isolates exhibited significantly lower biofilm inhibition (12.9% ± 7.4%) than agrII-negative isolates (33.0% ± 1.2%) at 100% v/v (P = 0.003). Nonlinear regression using a four-parameter log-logistic model generated distinct dose-response curves, with 95% confidence bands exhibiting minimal overlap (12.5%-100%). These findings suggest a potential association between agrII status and differential biofilm susceptibility to P. amboinicus extract. However, given the limited sample size and in vitro design, these results should be interpreted with caution. Overall, this study highlights the potential of P. amboinicus as an antibiofilm agent and supports further investigation of genotype-informed strategies against MRSA.