A simple and efficient strategy for iron-catalysed cascade radical cyclization was developed, by which an array of germanium-substituted indolo[2,1-a]isoquinolin-6(5H)-ones and indolin-2-ones were obtained in one pot with germanium hydrides as radical precursors. A rapid intramolecular radical trapping mode enabled the selective arylgermylation of alkenes over the prevalent hydrogermylation reaction.