Technical Abstract: Pear psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), a major economic pest of pears, have been shown to use a female-produced sex attractant pheromone. We compared the chemical profiles obtained from solvent extracts of diapausing and post-diapause winterform males and females, with goals to isolate and identify the pheromone. Post-diapause females produced significantly 13-methylheptacosane than post-diapause males and diapausing females. In olfactometer assays, males were attracted to synthetic racemic 13-methylheptacosane whereas females were not, indicating that the behavioral response to this chemical is sex-specific. Furthermore, 13-methylheptacosane was as attractive to males as a solvent extract of females, suggesting that this chemical was largely responsible for the female attractiveness. A field trapping study showed that males but not females were attracted to 13-methylheptacosane, confirming the olfactometer results. This study provides evidence through chemical analyses, behavioral bioassays, and a field experiment that 13-methylheptacosane is a sex attractant pheromone for C. pyricola winterform males. This is the first identification of a sex pheromone in the Psyllidae. Our results open the path to developing monitoring tools, and possibly new strategies for integrated pest management of this insect.