<p>In this study, we investigated pre-service teachers’ lesson designs, focusing on how they supported inquiry-based learning through problem posing activities. Our theoretical framework was based on Engeström’s activity theory through the lens of contradictions, and the data were analyzed using content analysis. The data were generated from a workshop on university campus, designed for a pre-service teachers’ mathematics course for school grades 5–10. Before the workshop, most pre-service teachers did not use problem posing activities in their lesson designs, and the level of students’ inquiry was low. However, during the workshop, a significant transformation occurred. All pre-service teachers revised their lesson plans to include problem posing activities, demonstrating active engagement in utilizing these strategies to meet the goals of the inquiry-based approach. Our findings highlighted the initial promise of problem posing to influence inquiry-based learning teaching practices and support the future professional development of pre-service teachers. Consequently, future research should investigate these dynamics across various educational settings to further refine and enhance the teaching practices employed in mathematics education.</p>