Constructivistic LKPD is a worksheet designed to give students the opportunity to express the ideas they have so as to encourage students to expand their knowledge regarding the problems given. This study aims to analyze how the students' conceptual knowledge using the constructivist student worksheets applied to the group investigation model. This research was conducted at SMA Dharma Pancasila Medan, this research is a quasi-experimental study where the sampling was carried out using purposive sampling, namely the sampling in the study was taken by consideration or certain criteria. The application of constructivist LKPD in the group investigation model was at the investigative stage. During the process of the investigation stage, a student skills assessment was carried out which consisted of seven indicators. The results of the student skills assessment showed a significant change in students' conceptual knowledge.