The current study investigated the impact of an integrated STEM collaborative approach embedded in a science methods course on early childhood and elementary preservice teachers’ pedagogical content knowledge (PCK) and curricular role identity for teaching science, as well as the potential relationship between these two constructs. Participants were recruited from a group of preservice early childhood and elementary teacher candidates (N = 65) completing an undergraduate teacher education program at a university in the southeastern United States. Using a mixed-methods design, the preservice teachers’ pedagogical content knowledge and curricular role identity were assessed using concept maps and a curricular role identity for teaching science survey (Forbes & Davis, 2008) at the beginning and end of the semester. Semi-structured interviews were conducted after the semester to collect qualitative data to clarify and explain the quantitative results. Findings suggested that the integrated STEM collaborative approach led to a significant increase in preservice teachers’ PCK and curricular role identity for teaching science over the semester. The significant increase was found in both early childhood and elementary education preservice teachers, with little to no departmental difference. There was no statistically significant relationship between the preservice teachers’ PCK and curricular role identity. Preservice teachers in this study found that examining science standards, unit planning, microteaching, and connecting with other teachers were beneficial for their development of PCK and curricular role identity for teaching science. This study affirms the collaboration among university faculty and preservice and in-service teachers. Implications and suggestions for future research are included.