A convenient and mild one-pot method for the synthesis of iodoarenes in high yields by the sequential diazotization-iodination of aromatic amines with a reusable polymeric diazotization agent in the presence of p-toluenesulfonic acid at room temperature in water was developed. The method is general and is the greenest alternative of the known diazotization-iodination methods. The method is also effective for the preparation of 1H-benzo[d][1,2,3]triazole and benzo[d][1,2,3]thiadiazole.