Vegetable oil with the advantages of biodegradability and low cost has been used as a plasticizer in the rubber industry. This study investigates the conditions of vegetable oil nanoemulsion as a plasticizer in natural rubber (NR) latex. Vegetable oil nanoemulsion with the particle size of 10.4 nm is prepared from blending coconut kernel oil/soybean oil, Tween 80 and water using phase inversion temperature method. The vegetable oil nanoemulsion is then added to NR latex. During the initial three days, latex particles have swollen, but subsequently they shrunk from 2673 to 1511 nm due to phase inversion. The result indicates that the tensile strength of latex films could be improved significantly with both higher incubation and vulcanization temperatures at 50 degrees C and 120 degrees C, respectively. Contact angle on the film surface is less than 90 degrees, showing that there is no oil blooming onto the surface.