The importance of programs that facilitate the transition of students to elementary school in order to support both their academic success and healthy development is undeniable. Therefore, the Ministry of National Education developed the School Adjustment Program in cooperation with UNICEF for first graders and implemented it in all elementary schools in Turkey. The aim of the present study is to examine the contribution of this program to school adjustment, student-teacher relations, peer relations, and various behaviors of elementary school students in first grade. The participants of the study, which is based on ex-post facto design, include 110 classroom teachers working in schools in Ankara during the 2015-2016 and 2016-2017 academic years. While 48 of these teachers implemented the adjustment program activities in their classrooms in 2015; others did not implement these activities in their classrooms in 2016. All the teachers filled in the School Adjustment Teacher Rating Scale, Student-Teacher Relationship Scale, and Child Behavior Scale (683 students engaged in the activities and 520 students did not) to evaluate how various aspects of their students' transition were affected by the program. One-way MANOVA analysis showed that the study group had higher mean scores for collaborative participation, liking school, self-directedness, and closeness to the teacher than the comparison group. Although the aggressive and prosocial behavior scores towards peers were higher in the study group, the partial effect sizes were found to be insignificant. While the scores of school avoidance and conflict with teachers were lower in the study group than in the comparison group, there was no difference between the groups in their scores for asocial behaviors towards peers, hyperactivity/distraction, anxiety/fear, and exclusion by peers. It was concluded that the program contributed to the establishment of close student-teacher relationships in the selected schools and the adjustment of the students to the schools.