The allylation of indigo results in the one-step synthesis of two unique complex heterocyclic systems: a spiroindoline–pyridoindolone arising from the addition of three allyl moieties and a fused pyridoindoloazepinoindolone generated from the addition and subsequent cyclisation of two allyl moieties. The structures of these novel heterocycles are assigned unambiguously using extensive NMR experiments and by X-ray crystallographic analysis. The distribution of the products is influenced by the use of thermal versus microwave heating.