Single-use technology is being widely adopted for the manufacture of biotherapeutics and cell therapy products. Rocked single-use bioreactors in particular have been commonly used, however, the hydrodynamics have rarely been characterized and are poorly understood. In this work, phase-resolved Particle Image Velocimetry and high frequency visual fluid tracking were used to investigate the flow pattern and velocity characteristics for the first time. The studies were performed on an optically accessible mimic of a Sartorius 2L CultiBag at different conditions. Wave formation was observed and higher rocking speeds caused the fluid to move proportionately out of phase with respect to the platform. Dimensional comparisons of fluid velocities with conventional bioreactors suggest that similar fluid dynamics characteristics can be achieved between rocked and stirred configurations. These results provide a first insight into the fluid dynamics of a novel bioreactor type at relevant process conditions supporting the generation of scale translation laws. (C) 2017 American Institute of Chemical Engineers