The purpose of this research was to explore whether playing self-hygiene serious game has any effect on the knowledge, self-efficacy, and behavior related to self-hygiene of young children. Three children, ages 5 and 6, all male, participated in this study. Three children were observed for one, two, and three weeks before game play. After this baseline period, the children were given a game titled Parasite Wars, in which the children have to kill the parasites to get healthy, to play for one week. After the initial exposure to the game, the children were observed during one week of game play for self-hygiene behavior. Also, immediately before and after the week of game-play, children were tested on knowledge and self-efficacy related to self-hygiene. Results indicate that all children improved in knowledge and self-efficacy after the gameplay. Numbers of voluntary hand-wash increased after initial exposure to the game for all three children. The numbers of verbal facilitation for hand-wash all decreased with game-play.