Disclosed herein is a metal-free, photochemical strategy for the direct alkylation of indoles. The reaction, which occurs at ambient temperature, is driven by the photochemical activity of electron donor-acceptor (EDA) complexes, generated upon association of substituted 1H-indoles with electron-accepting benzyl and phenacyl bromides. Significant mechanistic insights are provided by the X-ray single-crystal analysis of an EDA complex relevant to the photo-alkylation and the determination of the quantum yield (Φ) of the process.