The title compound, C(16)H(20)N(2)O(2), was synthesized from (S)-tryptophan methyl ester hydro-chloride and butyraldehyde. The absolute configuration 9S,10S was assigned on the basis of the unchanging chirality of the C9 centre. The NH group of the indole ring is involved in inter-molecular N-H⋯O hydrogen bonding, while the NH group of the six-membered ring is not. This latter ring has a half-chair conformation.