Although the evaluation field has increasingly integrated systems thinking and complexity science (STCS) into its work, little has been published on how capacity is built to do STCS‐informed evaluation. The chapter helps address this gap by exploring paired concepts drawn from the STCS and evaluation capacity building (ECB) literature: adaptive action and culture; boundaries and systems and structures; interrelationships and leadership; and perspectives and communication. The ideas are grounded with illustrative examples from a reflective case narrative of an international donor organization and the system surrounding it. Ultimately, the case shares how STCS can reimagine ECB and how increased capacity of the participants and organization can change the broader system.