This research aims to investigate the most frequent challenging behaviors faced by preschool teachers in their classrooms and the strategies and discipline approaches they adopt against these challenging behaviors. This research is conducted within case study design, which is a qualitative research method. The study group consists of 10 different preschool teachers teaching for children aged four-five in a city in the mid-south region of the United States. The research data was collected through one-to-one interviews performed by the researcher with the teachers. Content analysis was used to analyze the data obtained as a result of the interviews with the teachers. In the study, the challenging behaviors faced by the preschool teachers were asserted as the behaviors occurring under the themes of "accommodation problems" in the first place, followed by "self-control inadequacies" and then "absence of prosocial behaviors", and "deficiencies in assertiveness skills". The result of this study showed that preschool teachers mainly adopted multiple appropriate strategies which contribute to creating a warm classroom environment in their classrooms. It was stated that the discipline approach based on behavior change was mostly used as well as the instructional and effective communicational approach was partially used, while the assertive discipline approach was rarely used. It is recommended that the strategies and discipline approaches of teachers for dealing with challenging behaviors should be positively improved through supporting the knowledge, skills, and experiences of preschool teachers in the dimension of classroom management.