The apple clearwing moth, Synanthedon myopaeformis (Borkhausen) (Lepidoptera: Sesiidae), is a European species discovered in Cawston, British Columbia, Canada, in 2005. Using coupled gas chromatographic — electroantennographic detection analyses we identified candidate sex pheromone components in pheromone gland extracts and effluvia from calling females. Analysis of gland extracts using four gas-chromatography (GC) columns (DB-5, DB-17, DB-23, and DB-210) showed three components (A, B, and C) that consistently elicited strong responses from male antennae. Based on previous work, the most antennally stimulatory component, B, was hypothesized to be (3Z,13Z)-octadecadienyl acetate ((3Z,13Z)-18:OAc). Its retention time on the four GC columns and its mass spectrum in a concentrated extract matched those of an authentic standard, thus confirming structural assignment. Components A and C were below the detection threshold of the mass spectrometer, but their retention times on the four GC columns matched those of authentic standards of (3Z,13Z)-octadecadienol ((3Z,13Z)18:OH) and (2E,13Z)-octadecadienyl acetate ((2E,13Z)-18:OAc), respectively. Synthetic (3Z,13Z)-18:OAc, (3Z,13Z)-18:OH, and (2E,13Z)-18:OAc all elicited strong responses from male antennae, further supporting structural assignments of these three components. Of these antennally active compounds, only (3Z,13Z)-18:OAc and (3Z,13Z)-18:OH were detected in effluvia from calling female moths. In field trapping tests in Cawston, (3Z,13Z)-18:OAc alone was as attractive as, or more attractive than, binary or ternary blends containing this component. (2E,13Z)-18:OAc was behaviourally inactive alone or in combination with (3Z,13Z)-18:OAc, whereas 5% (3Z,13Z)-18:OH appeared antagonistic. Our analysis confirms that (3Z,13Z)-18:OAc is the major pheromone component in S. myopaeformis, and it alone is sufficiently attractive for use in detection surveys and development of pheromone-based controls for this introduced pest in Canada.