This study investigated the effectiveness of an integrated web-based portfolio system, namely the BOUNCE System, which primarily focuses on improving preservice teachers' reflective thinking skills. BOUNCE©, the software component of the system, was designed and developed to support a teaching practice model including a cycle of activities to be performed in teaching practicum courses. The effectiveness of the BOUNCE System was evaluated by investigating the development of preservice teachers' reflective thinking skills over time and the usability of the BOUNCE software. Preservice teachers demonstrated both high- and low-level reflective thinking indicators throughout the semester. A statistically significant change was detected in the number of high-level reflective thinking indicators from the first teaching experience to the second. Furthermore, the usability ratings of the BOUNCE© were above average. These findings highlighted the importance of integrated portfolio systems that combine technological and pedagogical elements to develop reflective thinking.