Sika deer (Cervus nippon) can severely affect natural vegetation and ecosystems. Wire fencing has been used to prevent damage, but this is generally unsuitable aesthetically for natural parks and landscaped grounds. Therefore, fenceless prevention methods are also required. We investigated the specific effect of capsaicin by using mimetic repellent non-capsaicin (experiment. 1), also the effects of different quantities of capsaicin repellent dispersion on deer (experiment 2). Five deer were used in these experiments. In experiment 1, four treatments were tested: for a control, the deer were fed from a feeding box containing hay cubes (HC); for the non-capsaicin treatment, mimetic pellets were mixed with HC in the feeding box; for the repellent treatment, repellent was mixed with HC in two quantities. The average amount of HC eaten was significantly greater for the control and non-capsaicin treatment (Holm test, P < 0.05) than capsaicin treatments. In experiment 2, six treatments were tested: the control was the same as experiment 1, HC; for the repellent treatments, repellent was mixed with HC in the feeding box in four different quantities; for the repellent-smell treatment, repellent was placed at the bottom of box and covered with wire under HC. The average amount of HC eaten was significantly greater in the control and repellent-smell (Holm test, P < 0.01) than the others. Our results showed that stimulus of capsaicin had an effect on eating behaviour of deer, and capsaicin repellent is effective when deer touch the product with their snouts.