Automated management of partition service assignment to a virtual input/output (VIO) adapter is provided. Responsive to creation of a new partition service in a data processing system, a partition priority number is determined for the new partition service, and, for each VIO adapter, the partition priority numbers of the partition services currently assigned to that VIO adapter are summed. For a VIO adapter with a lowest sum of partition priority numbers, logic determines whether assigning the new partition service to that VIO adapter results in its summed partition priority number being above a predefined threshold, and the new partition service is assigned to a VIO adapter based, at least in part, on whether assigning the new partition service to the VIO adapter with the lowest sum of partition priority numbers results in that VIO adapter's summed partition priority number exceeding the predefined threshold.