The purpose of this study was to investigate the effect of inquiry-based experiments on pre-service science teachers' science process skills. The study group consisted of 60 pre-service teachers in total, enrolled in the undergraduate program of Science Teacher Education, Faculty of Education at a state university. The study which used randomized quasi-experimental design with pre-test -- post-test and control group, designed as a mixed method study. Experimental practices were performed within a 10- week period. Science Process Skills Observation Form, developed by the researchers, was used as data collection tool in the study. IBM SPSS Statistics software was used for the analysis of quantitative data and content analysis was employed for analyzing the qualitative data. As a result of the analyses, inquiry-based experiments were more successful than confirmatory ones in terms of improving the science process skills of pre-service teachers. It is estimated that the results of this study will significantly contribute to the planning processes of teacher education programs as well as to the future studies on inquiry-based learning.