The title salt, C9H15N4O3 +·Br- [systematic name: 5-[(2S)-2-(3-azan-ium-yl-pro-pan-amido)-2-car-box-yl-ato-ethyl]-1H-imid-azol-3-ium bro-mide], contains four cations and four anions in the asymmetric unit. The dipeptide is a 'cationic zwitterion' with two localized positive charges and one delocalized negative charge. Two of the cations adopt an anti conformation for the non-hydrogen atoms of the -C(=O)-CH2-CH2-NH3 + grouping and two adopt a gauche conformation. In the extended structure, numerous N-H⋯O, N-H⋯(O,O) and N-H⋯Br hydrogen bonds link the components into (010) sheets and the structure is consolidated by weak C-H⋯O and C-H⋯Br inter-actions.