The solid-state structure of N-methylserotonin {systematic name: [2-(5-hydroxy-1H-indol-3-yl)ethyl](methyl)azanium hydrogen oxalate}, C11H15N2O+·C2HO4−, is reported. The structure possesses a singly protonated N-methylserotonin cation and one hydrogen oxalate anion in the asymmetric unit. In the crystal, the molecules are linked by N—H...O and O—H...O hydrogen bonds into a three-dimensional network.
