Two multifunctional lanthanide complexes, namely [Dy(HL)]·CH3OH (1) and [Er(HL)]·CH3OH (2), [H4L = N,N′,N′′,N′′′‐tetra(3,5‐dimethyl‐2‐Hydroxybenzyl)‐1,4,7,10‐tetraazacyclododecane] were synthesized and structurally characterized. Complexes 1 and 2 are isomorphic and crystallize in the non‐centrosymmetric orthorhombic space group Pca21. Their structure consists of one seven‐coordinated LnIII ion with the coordination geometry of trigonal prism, one HL3– ligand and one lattice methanol molecule. They exhibit second‐harmonic generation (SHG) effect. Complex 1 displays strong fluorescent emissions, which are typical narrow emission bands of lanthanide ions. In addition, complex 1 features field‐induced slow magnetic relaxation behavior. Therefore, complex 1 may be a potential multifunctional molecular material.