4D Flow shows clinical promise for a wide variety of cardiovascular applications. We hypothesized that flow measurements may be valuable across a variety of scanning parameters and field strengths typically used in clinical practice. We therefore established a multicenter clinical study at 4 sites using MRI in patients with atrial septal defects. We investigated the consistency of blood flow measurements obtained along the systemic and pulmonary vasculature. Quantitative data appear robust across multiple observers and measurement locations, from data obtained across multiple sites, representing a step forward in the implementation of 4D Flow in clinical practice.