It is significant to determine function of problem behaviors to develop effective interventions for behaviors demonstrated in preschool inclusion settings. This study aims to present the validity of trial based functional analysis (TBFA) method in determining the functions of behaviors for children with special needs and various problem behaviors who continue their preschool inclusion. Accordingly, TBFA's results are compared with the results of an effective method, traditional functional analysis (TFA), and consistency between these results are examined. In total, 4 male students between the months of 62-67, one with language disorder and three with autism spectrum disorders, participated in this study. Firstly, TBFA procedure, and secondly TFA procedure was applied. Data related to TBFA is collected through systematic observation, while multi-element design preferred in TFA. As a result, it is found that there is full consistency between TBFA and TFA to determine the functions of problem behaviors of all participants.