Team teaching is a popular and intense form of teacher collaboration with several advantages for both students and teachers. To successfully implement team-based practices such as team teaching, previous studies highlight the pivotal role of teachers' attitudes, which are subject to several personal and interpersonal processes. Stakeholders willing to implement team teaching require a deep understanding of teachers' attitudes toward the practice and their relation to prominent (inter)personal variables in teacher collaboration research. To date, however, little quantitative research exists on teachers' attitudes toward team teaching and even less on factors that may explain these attitudes. Therefore, the aim of this study is to explore how teachers value the implementation of team teaching in their teaching practices and to what extent prominent (inter)personal variables such as teachers' self-efficacy, perceived collaboration, and team similarity are associated with these attitudes. The empirical data were collected through a cross-sectional survey (N = 555) conducted in Flanders (Belgium). The findings showed that teachers had a positive overall attitude toward team teaching, but this was not always strongly expressed. In particular, teachers' attitudes toward enhancing the learning gains of students through team teaching were fairly neutral. Nonetheless, based on structural equation modeling, a proposed hypothetical model wherein self-efficacy beliefs, perceived collaboration, and team similarity were positively associated with teachers' attitudes toward team teaching showed adequate predictive validity. Furthermore, all three of the studied factors had a significant effect on teachers' attitudes, with teachers' self-efficacy exerting the strongest effect.