Abstract: Often in implementation science efforts, an intervention originated by research funding does not continue in clinical practice after funding ends, or if it does, the process by which it was sustained remains known only to the implementation research or clinical teams. From 2018 to 2020, we implemented a complex telehealth interdisciplinary behavioral health program supported by research funding. The intervention was Primary Care Mental Health Integration (PCMHI) delivered via televideo from a large parent medical facility to rural satellite clinics (tele-PCMHI) within the Veterans Health Administration. Two implementation facilitators worked closely with clinical leaders and staff to plan, launch, and sustain tele-PCMHI across four sites. The intervention is still maintained by the clinical service and has spread to eight sites. Based on ethnographic and qualitative data collected weekly over 2 years, we categorized sustainment strategies across distinct time periods for this complex program, theoretically grounded in the Dynamic Sustainability Framework, emphasizing changes to adapt intervention fit to rapidly changing context. To contextualize, we identified barriers and strengths, such as difficulty training staff to use new equipment, restructuring clinic workflow, and determining suicide risk management remotely. New barriers arose, and, thus, new strategies were needed to continue implementing at the onset of the COVID-19 pandemic in 2020. Different strategies at different stages of implementation allowed sustainment to be a dynamic and evolving process. Plus, proactive and persistent planning for sustainment early in the effort, along with alignment with performance metrics and national policy, supported continued delivery in real-world organized care.