Metal-organic network structure based on oxalate bridges {[MnIICrIII(oxalate)3]-}- and supramolecular cations (H2PPD2+)(benzo[18]crown-6)2[MnCr(oxalate)3](CH3OH)(CH3CN)2 (1) and (o-FAni+)2(DCH[18]crown-6)2[Mn(CH3OH)Cr(oxalate)3][MnCr(oxalate)3](CH3OH) (2), where H2PPD2+, o-FAni+, and DCH[18]crown-6 denote p-phenylenediammonium2+, o-fluoroanilinium+, and cis-syn-cis-dicyclohexano[18]crown-6, respectively, were synthesized. The crystal structure of 1 was the combination of [Mn(A)Cr(A)(oxalate)3]- and [Mn(A)Cr(Δ)(oxalate)3]-, whereas that of crystal 2 was the combination of [Mn(A)(CH3OH)Cr(Δ)(oxalate)3] and [Mn(A)Cr(Δ)(oxalate)3]. Large flexible supramolecular cations provide the three-dimensional structure of {[MnIICrIII(oxalate)3]-}-, which is different from the two-dimensional honeycomb structure often observed for {[MnIICrIII(oxalate)3]-}- complexes. Temperature-dependent magnetic susceptibilities of the complexes 1 and 2 exhibited ferromagnetic behaviors following the Curie-Weiss law (C = 11.5 cm3 K mol-1, θ = 13.0 K for 1; C = 4.14 cm3 K mol-1, θ = 12.3 K for 2).