A highly regioselective tetra-ortho-iodination reaction of perylene diimides (PDIs) has been developed, which could be conducted on a multigram scale (>10 g), featuring a column chromatography-free workup and purification. The ortho-iodinated-PDIs serve as key intermediates for the preparation of a variety of ortho-functionalized PDIs and PDI-based conjugated polymers.