In this study, the effects of STEM-based activities on students' motivation to learn science were investigated, and the opinions of students about the applied activities were also analyzed. The research group consists of a total of 98 eighth grade students studying in a state middle school in the 2018-2019 academic year. Six classes were included in the research, three experimental groups and three control groups were assigned randomly. The study process was carried out in a total of eight weeks while The Applications of Science. While teaching the experimental group with STEM activities, the control group was applied to the content of the curriculum of the science applications course. The groups were not affected by each other and equal lessons were given in all groups. The study was used as a semi-experimental design with the pretestposttest control group. In the research, "The Questionnaire for Motivation toward Science Learning" was used as a data collection tool, and "Semi-structured Interview Form" was used to determine the students' views on STEM activities during the application process of the experimental group students. The reliability coefficient of the scale used is 0.80. The semi-structured interview form was developed by the researchers. For the content validity of the questions in the form, ideas of two field education experts and one assessment and evaluation expert were taken. Analysis of the quantitative data collected from the questionnaire for motivation toward science learning made using the t-test for independent groups. Written answers of the students to the semistructured interview form were analyzed by content analysis, which is one of the qualitative analysis methods. As a result of the investigation, it decided that the motivation of the experimental group students was higher than that of the control group students. Additionally, students said that they had the pleasure while STEM activity applications.