A Lewis acid-catalyzed (3 + 2) cycloaddition of 2-indolylmethanols with β,γ-unsaturated α-ketoesters was established, which afforded a series of cyclopenta [b]indoles in overall high yields (up to 98 %) with excellent diastereoselectivities (up to > 95 : 5 dr). This reaction not only represents the first C3nucleophilic (3 + 2) cycloaddition of 2-indolylmethanols, but also provides a good example for (2 + n) cycloaddition of β,γunsaturated α-ketoesters, which will add new contents to the chemistry of 2-indolylmethanols. In addition, this approach provides an atom-economic and useful method for the construction of biologically important cyclopenta[b]indole scaffold.