Fumigant and contact toxicities of 11 Myrtaceae plant essential oils and their constituents against adult male and female Blattella germanica were evaluated. Of 11 Myrtaceae plant essential oils, Eucalyptus polybractea, E. smithii, E. radiata, E. dives, E. globulus, and Melaleuca uncinata, showed 100% fumigant toxicity against adult male German cockroaches at a concentration of 7.5 mg/liter air concentration. In contact toxicity tests, E. polybractea, E. smithii, E. radiata, E. dives, E. globulus, M. dissitiflora, and M. uncinata produced strong insecticidal activity against adult male and female German cockroaches. Of the essential oil constituents, terpinolene, α-terpinene, and terpinen-4-ol demonstrated strong fumigant toxicity against adult male and female B. germanica. Eugenol, isoeugenol, methyl eugenol, and terpinen-4-ol showed strong contact toxicity against adult male B. germanica. The toxicity of the constituent blends identified from M. dissitiflora essential oils indicated that terpinen-4-ol were major contributor to the fumigant activity or contact toxicity of the artificial blend. Only isoeugenol exhibited inhibition activity against male acetylcholinesterase. IC50values of isoeugenol were 0.22 mg/mL against male acetylcholinesterase.