Children play more vigorously and more productively when their teachers have formal education or training in the importance of play. Children with challenging play behavior in the play create a difficult situation for pre-service preschool teachers, affecting their achievement in the program objectives. Issues of challenging behavior in preschool classroom settings are, in part, related to teachers' self competencies of addressing these behaviors. The purpose of this study was to examine pre-service preschool teachers' self competencies of children's challenging play behaviors. It was found that the most difficult situation for pre-service preschool teachers were "kicking/biting" and "throwing toys." Besides physically aggressive behaviors, pre-service preschool teachers have not found themselves competent to get children's participation when "play is refused" by children. It is also found that pre-service preschool teachers had the most confidence level when children had difficulty in "expressing play progress" and when they did not help "cleaning up. "