The design and development of the supervisory and control system for an Electron Cyclotron Resonance (ECR) Ion Source at Laboratori Nazionali di Legnaro (LNL) are described. Both the hardware and the software architectures of the system are presented, together with its links with the control systems of the superconducting linear accelerator ALPI and of the new injector PIAVE. A number of different control devices and instruments for measurements are used in the ECR, and this feature forced the integration in the same system of both traditional home-made available hardware/software solutions and of commercial products for standard industrial control systems. The new control system for the ECR Ion Source is planned to be put into operation in some months. ©1999 American Institute of Physics.