The existence of helical flow in the superior vena cava (SVC) is not well understood in vivo. 4D flow MRI data of the SVC and brachiocephalic veins (BVs) were acquired in 8 healthy young males. SVC hemodynamic parameters, including velocity, pathlines, streamlines, and flow waveforms, were measured using a specialized post-processing software. Helical flow was present in the normal SVC. The flow pathlines from the right and left BVs formed helical flows, respectively, with two development types: twining and untwining. These findings may elucidate the occurrence and development of potential SVC disease.