A considerable body of research has suggested that without appropriate supports and learning opportunities on the job, beginning teachers are unlikely to develop effective instructional practices and find success. Informal supports, such as teachers' advice networks, have received less attention in research and policy yet can serve as substantial supports for teachers' development. In this study, we follow Baker-Doyle and define a teacher's intentional professional network (IPN) to be the set of people to whom the teacher chooses to go for advice or information about teaching. In this study, we investigated how first-year teachers participating in an alternative certification partnership were supported by different individuals over the course of their first year of teaching. In particular, we analyzed their IPNs, collected via survey, to understand exactly which individuals these first-year teachers sought out for advice or information about teaching and, using complementary interview data, investigated why the teachers included those individuals in their professional networks. In addition to reasons for selecting particular individuals within IPNs, we also discuss implications for designing and implementing formal supports for first-year teachers.