The present investigation was aimed to study in vitro anti-inflammatory and COX-2 inhibitory activity of Rosmarinus officinalis. For this study, 300 μg / ml and 500 μg / ml of petroleum ether, chloroform, ethyl acetate, methanol and water extracts were used. The extracts were obtained by successive soxhlet extraction. In vitro antiinflammatory activity was studied by membrane stabilization of HRBCs. The percentage of membrane stabilization was compared with standard drug Diclofenac sodium at a concentration of 300 μg / ml and 500 μg / ml. In vitroCOX-2 inhibitory activity was evaluated by enzyme immunoassay. Among the evaluated extracts, methanolic extract at a concentration of 500 μg/ml was found to show significant membrane stabilization of 84.27% and 74.59% of remarkable COX-2 inhibition. The results observed thus, suggest that the methanolic extract of dried leaves of Rosmarinus officinalis possesses promising in vitro anti-inflammatory and COX-2 inhibitory activities.