LAPOR as a general application of National Public Service Complaint Management System (SP4N), makes every central and regional government institution must integrate its complaints management system with LAPOR. But apparently, one of the institutions that experienced obstacles in its integration process was the Ministry of Environment and Forestry, which has many complaints systems. The integration process has been implemented since 2016. However, the integration process has not been fully successful yet in achieving its objectives. One of the causes encountered was symptoms of the silo mentality in the integration process. Therefore, this study aims to determine the characteristics and causative factors of silo mentality in the integration of the complaints management system in the Ministry of Environment and Forestry. This research is conducted using a post-positivist approach. The data are collected from in-depth interviews, observations, and literature studies. The results of the research showed that there were two main factors that led to the silo mentality in the integration of the complaints system in the Ministry of Environment and Forestry. These two factors are a lack of distribution of vision and mission and a lack of clarity on the roles and responsibilities of actors related to the integration of public service complaints systems in the Ministry of Environment and Forestry. While the dominant characteristic that shows the silo mentality is that each unit still prioritizes the safety and comfort of its unit and considers other units to provide additional burdens.