By using N,N‐dimethylformamide (DMF) as a methylenating reagent, the copper‐catalyzed C H activation of indole was demonstrated as an efficient and facile protocol for synthesizing 3,3′‐diindolylmethane (DIM) and its derivatives. The results indicate that copper chloride was the best catalyst among the investigated transition metal salts, which affords an excellent regioselectivity and good yield when tert‐butyl hydroperoxide (TBHP) was used as an oxidant.