This study aims to examine the effects of a course module aimed at improving pre-service mathematics teachers' (PMTs) proof schemes. This study used designed-based research. Participants of the course were 22 PMTs in a teacher preparation program. We obtained data from two surveys, one of which consists of proof questions. The other requires identifying the proof schemes of ten 9th grade students in a scenario including an excerpt of a hypothetical discussion with their teacher. We implemented both surveys before and after the intervention. In addition, semi-structured interviews were conducted with four PMTs. Findings indicated that the module had a significant and large effect on PMTs' proof schemes in favor of post-intervention. Most of the PMTs transformed their external and empirical proof schemes to the analytical ones. Findings also indicated that PMTs had difficulties identifying students' symbolic, example-based, transformational, and axiomatic proof schemes but overcame these difficulties after the intervention.