The purpose of this study was to investigate the effect of concept cartoon worksheets, gender and their interaction on pre-service science teachers’ conceptual understanding of geometrical optics. Participants were 121 sophomore students from four intact classes. A quasi-experimental design was used as the research method. The experimental group studied geometrical optics with implementation of concept cartoon worksheets prepared in consideration with a constructivist view of learning while the control group studied the lesson unit with traditional instruction. Students’ conceptual understandings of geometrical optics were measured by a tree-tier misconception test. The main effects of treatment, gender and their interactions on post-test scores were examined via ANCOVA test. The analysis yielded that the worksheets produced a statistically significant treatment effect; however, gender and gender*treatment interaction effect on students’ post-test performances were not significant.
