The research of the implementation of STAD cooperative learning in integrated science learning photosynthesis theme aims to describe the implementation science lesson plans, critical thinking skills, and student learning outcomes. The design of this study is "One Shot Case Study". Research goals is class VIII A SMP Negeri 2 Sugio Lamongan consisting of 24 students. Data collection methods used in this study are the observation method and testing methods. Observation method is used to analyze the implementation of learning and student activities (as supporting data), whereas the test methods used to analyze the critical thinking skills and student learning outcomes. Results of data analysis in this study include lesson plans implementation analysis, critical thinking skills, and student learning outcomes. Implementation of lesson plans observation during two meetings to obtain an average value of 3.15 with good category. Indicators of critical thinking skills are applied in this research includes interpretation, analysis, explanation, and inference. Critical thinking skills class VIII A varies with the details, 54.16% students have higher critical thinking skills, 29.16% had a moderate critical thinking skills, and 16.7% had low critical thinking skills. Mastery of student learning outcomes in this study (cognitive, affective, and psychomotor) was 83.3% with the details of the results of the cognitive aspects of learning throughout student average of 81 with very well category; psychomotor aspects of learning outcomes overall students average of 84 with category of highly skilled; affective aspects of learning outcomes overall students average of 77.25 with strong category. Keywords: integrated science, STAD, critical thinking skills.