Cooperative behaviors are very important for human lives, works and society in 21st century. It has been recognized by educators around the world that is a one of the most crucial factors for successful in complex problem solving and sustainable peaceful lives. This research was conducted in the context of Thai early childhood classroom. The objectives were to 1) compare the early childhood students’ scores of cooperative behaviors before and after the implementation of HighScope approach and to 2) analyze the early childhood students’ cooperative behaviors through the HighScope approach. Mixed research methodology was employed in this study. The pretest-posttest control group design was conducted mixing by the analytic description method. The experimental group consisted of 42 students from 84 students by cluster random sampling and the control group consisted of 42 students. They were studied in kindergarten during the first semester of the 2019 academic year at the Khon Kaen University Demonstration School. The research instruments consisted of lesson plans, cooperative behavior evaluation form, field notes, and a photo camera. Data were collected by 3 raters blind evaluating the students’ cooperative behavior, and 3 researchers taking field notes and photos. The data were analyzed by statistics (mean, S.D., t-test), and framework of Holz (2013). The results revealed that the experimental group students’ post- cooperative behavior score (mean = 3.71, S.D. = 0.06) higher than the pre-cooperative behavior score (mean = 3.45, S.D. = 0.06) with the statistical significance at the level of .01 and t-value of 5.46. Moreover, they demonstrated cooperative behaviors: social skills, expression of ideas, choice and decision making, feeling perception and conflict resolution, which are basis to form cooperative habit of mind. Teachers and educators could use HighScope approach to design instructional activities that promote students’ cooperative learning meaningfully