The interaction of triethanolamine (TEA) with Cu(II) salts of salicylic, cinnamic and succinic acids was studied for the first time. The structure of the synthesized complexes was investigated by single-crystal X-ray diffraction. TEA complexes with Cu(II) salicylate (1) and cinnamate (2) are binuclear mixed ligand complexes, but interaction of TEA with Cu(II) succinate leads to the formation of cationic mononuclear complex—[Cu(TEA)₂](C₄H₄O₄) (3). Cu(II) complexes 1–3 were also characterized by physicochemical and spectroscopic methods. Their antimicrobial activity was investigated.