Barbier-type allylation reactions of aldehydes and ketones have been carried out with both unsubstituted and γ-substituted allyl bromides using only a catalytic amount(0.1 equiv.) of In metal in [bmim][Br], but not in H₂O, organic solvents, or other room-temperature ionic liquids. The reactions did not require any metal activator and proceeded chemo- and regioselectively. The results of time-dependent ¹H NMR studies suggested that besides acting as a solvent, [bmim][Br] also acti-vates the In metal surface by electron polarization to generate both CH₂=CHCH₂–In (I) and CH₂=CHCH₂–InBr₂ (II) from allyl bromide and In. Of the active allylating intermediates, species II was regenerated by the in situ reduction of InBr₃ with an imidazolium-based N-heterocyclic carbene, both produced during the process, accounting for the catalytic action of the In metal.