This study aimed to investigate teachers' learning through researcher--teacher partnerships (RTPs). The theoretical framework, developed by Bannister, was applied to examine teacher learning in RTPs. Specifically, a case study of an RTP was conducted, in which university researchers collaborated closely with mathematics teachers. The data--including audio recordings of lesson-preparing discussions, lesson plans, videotaped lessons, and post-lesson interviews--were collected and analyzed to describe the case. It was found that the identity of the participating teachers changed from "problem posers and solution receivers" to "collaborative problem solvers" in the process of negotiating and finding solutions to practical problems with researchers within the RTP. Moreover, the selected theoretical framework was enriched by the inclusion of enactment and reflection.