[Objectives]  To develop a fast, accurate method for sexing the mature larvae, pupae and adults, of the Codling moth, Cydia pomonella (L.). [Methods]  Sexually dimorphic features of mature C. pomonella larvae, pupae and adults were photographed and measured under a microscope. [Results]  A distinguishing feature of mature male larvae was the obvious renal spots on the dorsum of the 5^th abdominal segment, which are absent in female larvae. Distinguishing features of male pupae include 4 distinct somatic lines behind the wing tip, and a longitudinal crack in the center of the ventral surface of the 9th abdominal segment with half round knobs on either side. Female pupae can be distinguished by 3 distinct somatic lines behind the wing tip and a lengthways crack in the front edge of the abdomen on the 8^th abdominal segment that connects to the abdominal line to form a "Y" shape. The sides of female pupae are also flat without protuberances. A distinguishing feature of adult males is a dark brown streak on the posterior edge of the ventral surface anterior of the ventral mid-chamber which is absent in females. The male abdomen is also long and narrow, and the valvae are often open, like a pair of pliers. In contrast, the female has a cylindrical abdomen with a tapered end. [Conclusion]  Sexually dimorphic features of mature larvae, pupae and adults of C. pomonella allow these developmental stages to be rapidly, and reliably, sexed.