A common approach to scaling up a professional development program is for the researchers who designed the program to prepare teacher leaders to facilitate it at their schools. When researchers eventually leave, however, teacher leaders may receive less support. To ensure that teacher leaders continue receiving support, researchers can prepare district mathematics specialists to assume responsibility for preparing the teacher leaders. Little is known, however, about district mathematics specialists' role in sustaining, and potentially adapting, professional development programs. We examined district mathematics specialists' facilitation of an adaptive teacher leadership preparation program. Program sessions were originally facilitated by researchers then by the specialists. We analyzed the adaptations specialists made to the sessions over four years and the rationales underlying these adaptations. Specialists maintained the program's overall structure, continuing to model the facilitation of core program activities that teacher leaders would then facilitate in their site-based professional development workshops. However, they modified the thematic focus of these activities to address district goals, interests, and priorities. Adaptations were informed by specialists' intimate knowledge of what was occurring in district schools. This approach maintained activities supportive of teacher learning, but also demonstrated that the specialists took increasing ownership over the program by adapting it.