The purpose of this action research class BK is to see group guidance services that can reduce student behavior in Class VII.A students of SMP Negeri 18 Mataram. The subjects of this study were students of class VII.A SMP Negeri 18 Mataram which consisted of 28 students consisting of 15 male students and 12 female students. Class determination is based on the level of problems that are owned in accordance with the results of discussions with fellow teachers conducted before the study, namely the low level of all students in the class who had skipped class and the frequency ranged from 9 to 15 times. The results of research on reducing behavior carried out through group guidance services for class VII.A students of SMP Negeri 18 Mataram in the 2018/2019 academic year are as follows: 1) Guidance services can be used as an effort to improve student behavior in schools. 2) Reduction of truancy behavior with treatment in the form of group guidance, the criteria were quite good (62.86%) in cycle I. After getting group guidance, the criteria increased to be high (85.71%) in cycle II thus, there was an increase of 22.85%. This increase includes the private category and negative truancy behavior. So it can be denied that group guidance is able to improve student truancy behavior at school. 3) The reduction of truancy behavior shows a significant increase after receiving guidance, which means that group guidance can improve truancy behavior at school.