Isodesmic C–H functionalization reactions are extremely rare. Herein we report the first Pd(II)-catalyzed isodesmic C–H iodination of arenes using 2-nitrophenyl iodides as the mild iodinating reagents. Unusual C–I reductive elimination occurred in preference to competing C–C coupling in this reaction. Assisted by aliphatic carboxyl directing groups, a range of hydrocinnamic acids and related arenes could be selectively iodinated at either meta- or ortho-positions of the phenyl ring. Remote diastereoselective C–H activation was also promising. This method may open up a new way to iodinate challenging substrates.