Public debate and scholarly discussions about a crisis of institutional trust focus on an external perspective: declining citizen trust, indicating that institutions lose legitimacy. While important, this perspective does not capture a conceptually distinct and politically salient form of institutional dysfunction occurring inside institutions that can undercut their trustworthiness. We develop an internal perspective on institutional trustworthiness. It focuses on the endogenous conditions under which officeholders are warranted in trusting that their interrelated actions can uphold institutional functioning. We argue that such warranted trust is grounded in the joint realization of two commitments: (1) to mutual accountability in exercising office power and (2) to the assumption of interrelated responsibility to uphold institutional action. We call the configuration in which these commitments are jointly realized “endogenous institutional trustworthiness.” We argue that endogenous institutional trustworthiness is irreducible to standard requirements of professional ethics. It is a distinct normative standard that specifies when officeholders are warranted in trusting one another under conditions of epistemic and normative uncertainty. This internal perspective matters for political theory because it reveals a specific form of institutional breakdown and identifies a corresponding target for institutional repair that cannot be seen from the external perspective alone.