An efficientcopper(I) iodide‐catalyzed sulfenylation of maleimides and related 3‐indolylmaleimides with thiols has been developed in the presence of fluoroboric acid. Several 3‐thiomaleimides and 3‐indolyl‐4‐thiomaleimides were obtained with good yields under ligand‐free conditions. The methods are simple, practical and show good functional group tolerance.