Two curved post-tensioned concrete wall assemblies were constructed and tested to delamination failure under monotonically increasing prestressing loads. In an effort to study the influence of size effect on the delamination failures observed, the nominal dimensions of the second specimen were twice those of the first, and the nominal reinforcement ratios of the two specimens were held constant. The data collected from the tests were used to investigate the underlying mechanics of the delamination failures observed and, to the authors’ knowledge, represent the first of their kind in open literature. The test results showed an apparent size effect on the delamination failures of the curved wall assemblies. Furthermore, the compressive stresses at the onset of the first delamination crack were found to be on the order of approximately 0.13fc′ to 0.23fc′, which is significantly lower than the stress limit of 0.35fc′ permitted for service load conditions as specified in ACI 359-15. Finally, the friction losses based on ACI 343R were found to underestimate the measured friction losses by approximately 38 to 43%.