Cyanoacetamidobetaine, or N-cyano-2-(trimethylammonio)acetaminide, is obtained from a reaction of sodium dicyanamide and betainium chloride in an aqueous solution after 4 h at 30 °C. By adding DCM, single-crystals suitable for diffraction experiments are obtained. The compound crystallizes in the monoclinic space group P2₁/c with lattice parameters a = 7.3365(2) Å, b = 8.8351(3) Å, c = 11.0977(4) Å, and β = 91.948(2)°. The unexpected reaction product comprises a trimethylammonium head group linked via a methylene bridge to a negative cyanoacetaminide moiety, highlighting the thermodynamic preference for intramolecular charge compensation over salt formation of betainium with dicyanamide. The findings are supported by infrared and nuclear magnetic resonance spectra and density functional theory calculations.