Cinnamon (Cinnamomum burmannii) is a species of plant that produces essential oil known as cinnamon oil. The cinnamon oil has been used as antibacterial and anti-inflammatory agents. The essential oils are not soluble in water. Therefore, their application into food products is limited. An approach that can be done to overcome this problem is by incorporating essential oils into a nanoemulsion system. This research aimed to optimize the emulsification process of the cinnamon oil nanoemulsion by varying the emulsifying condition, i.e., homogenization speed, time, pressure, and cycles. The physicochemical properties and stability of cinnamon oil nanoemulsion were observed. The homogenization process with a speed of 14000 rpm for 3 minutes produced cinnamon oil emulsion with droplet size 10.40 μm and polydisperdibility index (PDI) of 0.901. The homogenization process at 500 bar using high-pressure homogenizer with three cycles produced cinnamon oil nanoemulsion with droplet size ± 117.5 nm and polydispersibility index (PDI) of 0.123. The droplet size of nanoemulsion during storage at 4 ± 2 °C, 28 ± 2 °C, and 40 ± 2 °C for three months did not change the droplet size (P<0.05). The minimum concentration to inhibit S. aureus and E.coli was similar for bulk, coarse emulsion and nanoemulsion of cinnamon oil. However, cell count after the two bacteria tested at 37 °C incubation for 24 hours showed that the highest number of bacterial cells was in bulk cinnamon oil, followed by the coarse emulsion and lowest number of bacterial cells was in cinnamon oil nanoemulsion. This indicates that cinnamon oil nanoemulsion has a higher antibacterial activity than coarse emulsion and bulk cinnamon oil.