. This study aimed to determine the effect guided inquiry learning model toward learning outcomes of students in XI MIPA classes at SMA Negeri 1 Sindangkasih on nervous system subject. This research was conducted from September 2018 until July 2019 at SMA Negeri 1 Sindangkasih. The research used the true experiment method. The population in this study were all XI MIPA at SMA Negeri 1 Sindangkasih as many as 3 classes. The sample used was 2 classes, namely class XI MIPA 1 as the experimental class and class XI MIPA 3 as the control class taken by cluster random sampling technique. Data collection techniques in the form of tests of learning outcomes on the nervous system subject was conducted before and after learning process were taken place. The datas were analyzed by using the Ancova test. The results showed that there was the effect guided inquiry learning model toward learning outcomes of students on nervous system subject in XI MIPA classes at SMA Negeri 1 Sindangkasih.