The qualitative research employed semi-structured interviews with 28 elementary school teachers to examine the types of knowledge they use to integrate digital game-based learning (DGBL) into their classrooms and the nature of their integration planning. The findings revealed that teachers use four types of knowledge: game knowledge, game technological knowledge, game pedagogical knowledge and game technological pedagogical content knowledge. Five integration planning stages were identified, with stages A-C concerning the process of game selection and stages D-E concerning the integration of games in the classroom. Most teachers plan DGBL integration into their classrooms using a structured approach that follows each stage in order, whereas some teachers adopt a flexible planning pattern that omits or reorders some stages. The types of knowledge teachers use at each DGBL integration planning stage were identified and will be relevant to teacher educators and to teachers seeking to better integrate DGBL into their practice.