The transition from pre-service to beginning teaching has been well documented as complex and challenging, with novice teachers shown to experience a number of professional highs and lows throughout their first year of teaching. As they reflect on early experiences, beginning teachers establish perceptions of causality that influence their sense of professional agency, self-efficacy and motivation. This attributional thinking can have a strong impact on their ongoing development as teachers. In this chapter, which reports on the first phase of a larger mixed methods study, we discuss the influence of attributional thinking on the development of beginning teachers’ professional learning identities. The use of an online survey, drawing from a sample of 57 beginning teachers working in independent schools across Queensland, sought to identify the ways in which participants attributed causality (that is, why things happened the way they did) for their professional highs and lows during their first year of teaching. The study found that, when attributing causality for success, participants were most likely to identify their own practice as an enduring cause for this and similar future successes. They were also likely to attribute causality for events perceived as unsuccessful to their own practice. Notably, this study found that beginning teachers apportioned high shared levels of control of causes for both successful and unsuccessful events with others, such as their colleagues and mentors. This study raises significant questions as to how attributional thinking, engaged during reflective practice, impacts the development of the professional learning identities of beginning teachers.