Although multilingual learner (ML) students are present in nearly all K-12 settings, they tend to be served by schools and educators who are inadequately prepared to support them. While state education agency leaders may be well-positioned to address inequities in ML education, given their roles as policy intermediaries, their work is politically complex. Further, professional development support for state-level leaders has historically been limited. Research-practice partnerships (RPPs) represent a promising avenue for addressing this absence in state leadership support, as RPPs aim to promote educational transformation through collaboration between researchers and practitioners. In our case, we posit that state-education-agency leaders' engagement in a cross-state RPP has the potential to support enactment of "transformative-leadership practices", specifically through opportunities to think and work with role-alike colleagues and external researchers. Drawing on qualitative case study methods, our findings reveal how ongoing RPP collaboration in small groups supported state leaders' enactment of transformative approaches, such as developing a statewide framework for ML education and supporting district leaders with using ML-specific funds in equity- and evidence-based ways. Findings shed light on specific RPP activities that supported leaders' collaboration, which may inform how future partnerships are facilitated to advance equity-focused change efforts.