Free inquiry is one level in inquiry learning that encourages students to identify a problem, find solutions to these problems through an experiment that was designed independently. One of the learning activities that can be applied is mini research. The purpose of this study was to investigate the effects of environmental pollution based mini research on integrated science process skills of students. This study uses a control class (laboratory activities) and the experimental class (mini research), both administered through learning activities about environmental pollution. This study is a quasi-experiment which sampling was taken by purposive sampling and using the matching-only design pretest-posttest control group design, in which the control and experimental classes are given a pretest and posttest. The subjects were high school students who took the specialization class, X Mathematics Natural Sciences (MIPA) in a country SMAN in Majalengka. Students from two classes, respectively accounted for 36 and 37 people. The data were taken by using integrated science process skills test, performance assessment of mini research, and students' questionnaire responses concerning the application of learning that includes an ntegrated science process skill. The results showed that there were significant differences in integrated science process skills of students between the experimental class and control class. Assessment of performance mini research also showed good results, accompanied by a good response also to a mini lab activities and research in which students learn to apply the scientific approach.