Team-based care enhances accurate diagnosis in hospitalized patients. In addition to formal inter-professional collaboration, such as specialty consultation, many hospitalists use informal strategies, such as peer diagnostic second opinions. Little is known about this practice. We conducted a cross-sectional survey among hospital medicine physicians and Advanced Practice Providers at 13 hospitals. We assessed the frequency of requesting and providing peer second opinions, comfort discussing diagnostic uncertainty, and perceived barriers to second opinions. 338 hospitalists responded. Half (51.5%) reported routinely seeking a second opinion when facing diagnostic uncertainty. 98.2% felt psychologically safe discussing uncertainty, and 97.3% believed second opinions improved diagnostic accuracy. The most common barriers to seeking a peer-second opinion were time constraints (64.3%) and fear of bothering colleagues (56.6%). Less experienced hospitalists were more likely to report vulnerability as a barrier (39.2% vs. 26.8%, p = .03). Strengthening systems that facilitate peer consultation and support junior clinicians could improve diagnostic collaboration and accuracy.