We describe a method for determining the sex of sika deer (Cervus nippon yesoensis) from feces collected in the field. Using a nested polymerase chain reaction (nested PCR), partial sequences of the sex determination region of the Y chromosome (SRY) gene and X zinc finger protein (ZFX) gene were amplified. In 19 individuals with sex information, the correct sex was successfully detected and sequences of target amplicons were completely matched between muscle and feces from the rectum. Among 75 fecal samples collected noninvasively in the field, 68-71 samples (90.7-94.7%) yielded successful sex determinations. Using this technique, feces collected in the field would enhance the utility of genetic analysis. As a result, instead of biomaterials, these samples can serve as new or alternative materials. Finally, it can be expected that this technique will contribute to reveal in advanced detail of the population dynamics and genetic diversity that needed to carry out effective population control and to reduce the extinction risk of sika deer.