Two crystalline salts have been obtained from the system l-serine - picric acid - H2O: l-serinium picrate monohydrate (I) and tris(l-serine) bis(l-serinium) dipicrate trihydrate (II). The salt (I) crystallizes in monoclinic system (space group P21, Z = 4). Asymmetric unit of (I) contains two formula units. Carboxyl groups of both l-serinium cations form hydrogen bonds with picrate anions with O···O distances: 2.595 (6) Å and 2.638 (5) Å. The salt (II) crystallizes in orthorhombic system (space group P212121, Z = 4). Asymmetric unit of (II) contains one formula unit. Carboxyl groups of both l-serinium cations form short O-H···O hydrogen bonds with two of three zwitterionic moieties, forming two dimeric (l-serine l-serinium) cations with O···O distances: 2.485 (3) Å and 2.487 (3) Å. The infrared and Raman spectra of obtained salts are recorded and discussed.