We aimed to validate a method to identify age class and sex of sika deer (Cervus nippon), which defecate fecal pellets. We collected 42 and 54 fecal samples in Nara and Yakushima, respectively. Both pellet width and length were significantly larger for adults than juveniles (1∼1.5 yrs). A discriminant model based on both width and length correctly assigned an age class for 92% of individuals in Nara and 98% in Yakushima. We genetically determined their sex based on the gel electrophoresis of two genes on sex chromosomes (SRY and ZFX/Y) amplified by PCR. For fresh feces, sex was not determined for 40% of the samples, but for the rest of the samples, sex was correctly assigned in almost all cases (28/29). However, sex was not determined in any of the samples that were analyzed at a half month or later after defecation. The proportion of young individuals could be estimated by the morphometry of fecal pellets, but the sex of the animals could not be confirmed.