This study aims to examine the lesson plan development processes and related experiences of prospective teachers, and determine the potential effects their lesson plan development efforts on their perceived TPACK. The research was conducted as part of a 14-week Mathematics Teaching course. During the course, prospective teachers underwent a six-week training program focused on designing technology-supported mathematics lessons, followed by an eight-week period dedicated to developing lesson plans for different topics and objectives within the mathematics curriculum. Data for this case study was collected from sample of 44 prospective teachers through participant diaries, observation notes, interviews, and pre- and post-lesson administration of the Turkish version of Schmidt et al.'s (2009) TPACK scale. Qualitative data was thematically analyzed to complement quantitative analysis using a t-test. The findings indicate that engaging in lesson plan preparation activities during mathematics teaching courses positively influenced prospective teachers' perceived TPACK levels. Specifically, an increase in TPACK levels was observed after attending the course. Furthermore, several factors have been identified that enable prospective teachers' perception of TPACK to be positively affected. These findings suggest the need for technology-supported course design within the mathematics curriculum of teacher training programs. Providing elective courses that offer prospective teachers additional opportunities to develop lesson plans is recommended.