The function of a teacher is to form and give the outcome of students’ participation in the teaching and learning process. The teachers also could improve morale, motivate, and guide students to obtain a high achievement of education. Thus, the researcher is wondering whether there is an impact of teachers’ behavior towards students’ academic achievemeng in teaching and learning process. The aims of this research were to know (1) the teachers’ behavior of in one of Islamic University in Yogyakarta, (2) the students’ academic achievement, and (3) the impact of teachers’ behavior toward students’ academic achievement in teaching and learning process. The data were collected from 118 students’ batch 2015. This research used the questionnaire that adapted from Keeley and Buskist (2006) on Teacher Behavior Checklist with the reliability 0.875 which means it is highly reliable. The result of this research showed that the teachers’ behavior was good category as it was shown by the mean 89.6. On the other hand, students’ academic achievement belongs to Good – Extensive Achievement (B+, B, B-) category with the mean 3.2. In addition, the last result showed that the value of significance (sig) is 0.831 higher than probability 0.05, which means that there is no a significant impact between teachers’ behavior (x) towards students’ academic achievemnt (y).