The bacterial tubulin FtsZ is the central component of the cell division machinery, coordinating an ensemble of proteins involved in septal cell wall synthesis to ensure successful constriction. How cells achieve this coordination is unknown. We found that inEscherichia colicells, FtsZ exhibits dynamic treadmilling predominantly determined by its guanosine triphosphatase activity. The treadmilling dynamics direct the processive movement of the septal cell wall synthesis machinery but do not limit the rate of septal synthesis. In FtsZ mutants with severely reduced treadmilling, the spatial distribution of septal synthesis and the molecular composition and ultrastructure of the septal cell wall were substantially altered. Thus, FtsZ treadmilling provides a mechanism for achieving uniform septal cell wall synthesis to enable correct polar morphology.