The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission conducted nearly two years of proximity operations around asteroid (101955) Bennu. Optical navigation (OpNav) was critical to the success of OSIRIS-REx’s mission to collect a sample from asteroid Bennu. Landmark-based OpNav was particularly important for achieving the highest precision mission requirements. This paper assesses the performance of the landmark OpNav after the transition from centroid-based OpNav at the end of the Orbital A phase. An overall evaluation of the landmark performance is presented as well as analysis of potential sensitivities to viewing conditions and a priori state information.