This study examines the use of a virtual internship (an epistemic game) for developing preservice teachers' technological pedagogical content knowledge (TPACK). TPACK aims to capture the essential qualities of teacher knowledge that are needed for integrating technology into teaching. Virtual internships are computer-based professional practicum simulation games where participants assume the role of a professional, work collaboratively on authentic tasks, and engage in complex professional thinking. The online collaborative chat records of 33 preservice teachers who played the game over the course of 8 weeks were analysed using epistemic network analysis (ENA), which made it possible to examine the dynamic connections between various TPACK domains over time. The analysis showed that participants' TPACK representations gradually became more complex in terms of the number of pedagogical considerations and the strength of connections between pedagogical considerations, technology, and content. Suggestions are made for designing learning environments that aim to develop preservice teachers' TPACK. Implications for practice or policy: (1) Findings suggest that virtual internships are an effective means of developing preservice teachers' TPACK; (2) Teacher educators can use this knowledge when designing learning environments not only to develop preservice teachers' TPACK but also other forms of teacher professional knowledge; (3) ENA affords an innovative way to assess TPACK development; and (4) TPACK can be framed as an epistemic frame, which could better align with its conceptualisation.