Dendropanax morbifera is a versatile plant that has been used as a herbal medicine due to its various useful medicinal effects. To protect its active component from biological stress and increase its drug efficacy as well as drug bioavailability, nanoemulsion was prepared. Dendropanax morbifera zinc oxide nanoparticles (DM-ZnO NPs) were synthesized using the plant extract via the co-precipitation method and loaded with active indole-3-carbinol for nanoemulsion formulation using the ultrasonication process. Field emission transmission electron microscope revealed the flower shape of the Dendropanax morbifera indole-3-carbinol zinc oxide nanoemulsion (DM-ZnO-I3C-NE). In contrast, DM-ZnO NPs showed a spheroid shape that coincides agreeably with field emission electron scanning microscope. The hydrodynamic sizes by dynamic light scattering are about 65 ± 3 nm and 239.6 ± 6 nm and the crystallite sizes from X-ray diffraction are 11.52 nm and 16.07 nm for DM-ZnO NPs and DM-ZnO-I3C-NE, respectively. In vitro analysis revealed the cytotoxicity of DM-ZnO-I3C-NE against a human lung cancer cell line (A549) at 12.5 µg/mL as well as reactive oxygen species (ROS) production. The DM-ZnO-I3C-NE-induced ROS generation level was higher than that of DM-ZnO NPs and free indole-3-carbinol. The synergistic effect of DM-ZnO and indole-3-carbinol indicates DM-ZnO-I3C-NE as a potential candidate for future lung cancer drug and could be scope for functional food.