The biocidal activity of three steam distilled wood essential oils—incense cedar, Calocedrus decurrens (Torr.) Florin; Port-Orford-cedar, Chamaecyparis lawsoniana (A. Murr.) Parl.; and western juniper, Juniperus occidentalis (Hook)—were evaluated against adult Aedes aegypti (L.) (Diptera: Culicidae) and Xenopsylla cheopis (Rothchild) (Siphonaptera: Pulicidae) and nymphal Ixodes scapularis Say (Acari: Ixodidae). In vitro laboratory bioassays were conducted to establish baseline dose–mortality data through 24 h. Incense cedar heartwood was the most toxic to all three vector species followed in order of activity by western juniper and Port-Orford-cedar based on LC₅₀ and LC₉₀ values. Ae. aegypti were substantially more susceptible to the oils than either I. scapularis or X. cheopis.