In the present study, viscozyme L pre-treatment for aerial parts of Rosmarinus officinalis L. (rosemary), grown in Lam Dong province, was performed to evaluate the effective extraction of essential oils by hydro-distillation. Enzymatic pre-treatment with 1 g viscozyme L enzyme mixed with 5 mL sodium chloride 15% at 50^oC for 1 hour, followed by hydro-distillation, was seen to slightly increase the yield of rosemary essential oils from 0.96% to 1.08%. GC/MS analysis showed the presence of 32 compounds in rosemary essential oils, of which the major components were α-pinene (29.71 - 32.17%) and cineol (17.55 - 18.74%) in both the control and the enzymatically treated samples. The results also revealed that rosemary essential oils obtained from both the control and the enzymatically treated samples exhibited moderate antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans in all tested concentrations.