Teacher collaboration is widely endorsed across the teacher continuum, including student teachers, due to its positive impact on teachers’ professional practice, knowledge and support, and learner outcomes. Notably, one’s definition of teacher collaboration informs beliefs and engagement in the process. Yet, little attention has been given to student teachers in this regard. Employing Broaden-and-Build theory (BBT; Fredrickson, 2004), this case study examines student teachers’ understanding and the perceived impacts they align to the teacher collaboration. 119 student teachers in one Initial Teacher Education (ITE) institution, in the Republic of Ireland completed a researcher-designed questionnaire seeking their definition of teacher collaboration and aligned impacts they afford to the process. Thematic analysis revealed participants’ understandings of collaboration included working together, sharing and a school-wide activity. Participants were positively disposed to collaboration, with enhanced intellectual, social and emotional resources attributed to collaborators. Inhibitory factors, such as lack of understanding, limited time and problematic working relationships were also identified as restricting collaborative opportunities and by extension associated gains. Discussion of the findings and their support of BBT are presented, as well as future research emanating from this study considered.