N-Methylpiperidine betaine (MPB) and L(+)-tartaric acid form a six-molecular non-centrosymmetric crystalline complex through two OAHÁ Á ÁO@C and four COOÁ Á ÁHOOC hydrogen bonds. The structure of this co-crystal has been determined by X-ray diffraction. The molecular structure of the title compound has been studied by FTIR, Raman and NMR spectroscopies and calculations by the B3LYP/ 3-31G(d,p) level of theory. This co-crystal belongs to the monoclinic system, space group P2 1 with a = 10.2691( 4), b = 9.4528(3), c = 24.0637(7) A ˚, b = 98.227(3)°, Z = 2, R = 0.026. Two molecules of TA and four molecules of MPB form a six-membered, asymmetric, hydrogen-bonded cluster, [(MBP) 2 TA] 2 . The core of the cluster is formed by two TA molecules linked by OAHÁ Á ÁO@C hydrogen bonds of the lengths 2.786(1) and 2.761(1) A ˚, into a cyclic asymmetric dimer. Four MPB molecules are bonded to the TA core by four COOÁ Á ÁHOOC hydrogen bonds of the lengths 2.493(1), 2.496(1), 2.511(1) and 2.512(1) A ˚. The piperidine ring has a chair conformation, however, the CH 2 COO À substituent at the nitrogen atom occupies the opposite positions (axial and equatorial) in MPB moieties bonded to each TA. The clusters are bonded into infinite chains, parallel to the y-axis, by the OAHÁ Á ÁO@C hydrogen bonds of 3.051(1) A ˚. In the optimized structure of the title complex the fragments of (MPB) 2 TA in the cluster are twisted, which causes a shortening of the intermolecular hydrogen bonds between the TA molecules. The FTIR spectrum is consistent with the X-ray structure.