The complexation of the bismalonamide ligand 2,2′‐[1,2‐phenylenebis(methylene)]bis(N,N,N′,N′‐tetraethylmalonamide) (L), bearing two C‐alkylated N,N,N′,N′‐tetraethylmalonamide groups, onto an ortho‐xylylene [C6H4(CH2)2] platform with trivalent lanthanides was investigated, both in solid and solution states. The crystal structures [Nd2(NO3)6L2]·(CH3CN)3 (2), [Nd2(NO3)4L2]·[Nd(NO3)5]·(CH3CN)1.5 (3), Ce(NO3)3L2 (4), and [NdL2]·(ClO4)3·C2H5OH (5) were analyzed by single‐crystal X‐ray diffraction. The ortho‐bismalonamide (L) is tetradentate in structures 2, 3, and 5 and bidentate in 4 only. It was found that structures 2 and 3 are composed of dimeric species. According to electrospray‐ionization mass spectrometry, the dimers are prevailing in acetonitrile solutions. The polydentate coordination of the ortho‐bismalonamide (L) with trivalent lanthanides suggests that an entropy effect favors liquid–liquid extraction of metal ions with this type of ligand.