Previous research reports mention several learning models which are potential in improving students’ thinking skills. This quasi-experimental research aims to determine the difference in critical thinking skills of the students who learned by using inquiry-discovery model and conventional learning model in class X. The treatment of this research was teaching physics by inquiry-discovery model and conventional learning model. The instruments of critical thinking skills were developed by the researcher and validated by an expert prior to use. The results of the research showed that there was a significant difference in the critical thinking skills between the experimental class and the control class. The result of critical thinking skills of the students in the inquiry -discovery class was higher than that of the conventional learning class. The research recommends that teachers empower HOTS ability of the students in the inquiry-discovery class, so that a meaningful learning and student-centered learning can be created. Future researches are needed to explore the contribution of inquiry-discovery model on students’ critical thinking skills.