Teacher collaboration is an important feature of job satisfaction and self-efficacy for teachers. Moreover, the collaboration of teachers is important for adopting professional changes as professional development (PD) activities that include opportunities for collaboration have been shown to support teachers in improving classroom practice. This may even lead to higher student performance. Situated in the context of the Advanced Placement (AP) reform in the United States, we investigated the perceived importance of opportunities to collaborate with colleagues as a rationale to participate in PD (N = 3,725 teachers). The opportunity to collaborate with colleagues was a primary rationale why teachers selected PD activities. While this rationale is only slightly related to school and teacher characteristics, it was related to PD characteristics. Specifically, opportunities to collaborate with colleagues were important to teachers in selecting informal face-to-face (FtF) PD activities. We conclude that collaborative structures benefit all forms of teacher professional development.