Six plant essential oils, vanillin, and their mixtures were tested for repellent activities and olfactory responses in a dengue virus vector mosquito, Aedes aegypti. Among the plant essential oils, cassia oil showed complete protection time (CPT) of 75 minutes. CPTs of lemongrass, lemoneucalyptus, xanthoxylum oils, and vanillin were within 30 minutes at 5% (0.21 mg/cm2) tested level, although their CPTs were not comparable to same concentration of DEET that showed 127.5 minutes of CPT. However, their repellency effects were significantly improved in two conditions; improving concentration up to 15% level (0.63 mg/cm2) and addition of vanillin. In bioassays using binary or tertiary mixtures with one or two essential oils with or without vanillin, the composition of 1:3:1 (v/v/w) consisted of lemongrass oil, xanthoxylum oil and vanillin provided 270 min-CPT. As a practical application, the mixture of 1:1:1 formulation containing lemongrass oil, xanthoxylum oil, and vanillin (v/v/w) was enclosed into the Viscopearl, porous cellulose beads that provide gradual release of volatile compounds. Efficiently, more than 90% of repellency for 2 hours was observed in cage and semi-field chamber tests using the formulation. In addition to behavioral assays, we subsequently examined how mosquitoes sense the blends of oils with vanillin by using electroantennogram (EAG) recording. Binary mixture with one oil and vanillin, which extended CPTs, showed no significant patterns of EAG alternation, while tertiary mixtures of oils and vanillin decreased patterns of EAG responses as an increase of vanillin contents in the mixture, implying further potential roles of vanillin as a synergist in mosquito repellency. Based on behavioral and electrophysiological data, cassia, rosemary, lemongrass, xanthoxylum, and lemoneucalyptus oils could provide the high possibility for development of commercial products for useful management strategies to control mosquitoes.