A common problem with 4D flow magnetic resonance imaging is aliasing that occurs as a result of a low velocity encoding parameter. Consequently, an efficient and robust algorithm is needed to unwrap this data. We propose an iterative graph cuts algorithm to perform the necessary phase unwrapping and attain correct velocity values. The graph cuts algorithm utilizes a global energy minimization framework. This method is shown to accurately unwrap the aliased data more accurately than existing techniques for 4D Flow data. This included unwrapping synthetic data with Vencs down to 20% of the max velocity and SNRs down to 2.