Science process skill (SPS) is very important for developing science concept knowledge and scientific attitude. This skill was a challenge for pre-service science teachers, especially in the Indonesian curriculum. Thus, pre-service science teachers require SPS to implement science learning using the inquiry module. This study aims to investigate the Science Process Skills (SPS) of pre-service teachers in Environmental Education classes, based on groups, gender, and educational streams through open ended and guided inquiry modules. 204 pre-service science teachers participated in this quasi-experimental design namely “non-equivalent control group design” using open-ended inquiry module, guided inquiry module, and conventional module. Using Two-way ANOVA, MANOVA and MANOVA factorial 3x2 analysis, the results revealed that there were statistical significances found at p=0.00 of SPS based on the groups. Meanwhile, the analysis of statistics based on gender (p=0.70) and the educational stream (p=0.70) reveals no significant difference. There were also no significant differences in theMean score test of SPS constructs based on educational stream and groups. These findings indicate that open-ended inquiry and guided inquiry modules can enhance pre-service teachers’ SPS. The implication of this study leads to the suggestion of the enhancement of SPS pre-service teachers by usinginquiry-based learning. Keywords: ScienceProcessSkill,Pre-ServiceScienceTeahcers,OpenEnded