Two new isostructural complexes, namely, poly[aqua[μ3-2-(4-carboxyphenoxy)terephthalato-κ3O1:O4:O4′](1,10-phenanthroline-κ2N,N′)cobalt(II)], [Co(C15H8O7)(C12H8N2)(H2O)]n or [Co(μ3-Hcpota)(phen)(H2O)]n, I, and poly[aqua[μ3-2-(4-carboxyphenoxy)terephthalato-κ3O1:O4:O4′](1,10-phenanthroline-κ2N,N′)nickel(II)], [Ni(C15H8O7)(C12H8N2)(H2O)]n or [Ni(μ3-Hcpota)(phen)(H2O)]n, II, have been synthesized by solvothermal reactions. Complexes I and II were fully characterized by IR spectroscopy, elemental analyses, thermogravimetric analyses, and powder and single-crystal X-ray diffraction. They both present two-dimensional structures based on [M2(μ-COO)2]2+ (M = CoII or NiII) dinuclear metal units with a fes topology and a vertex symbol (4·82). Interestingly, the positions of the two dimeric metal motifs and the two partially deprotonated Hcpota2− ligands reproduce regular flying butterfly arrangements flipped upside down and sharing wings in the ab plane. Magnetic studies indicate antiferromagnetic interactions (J = −5.21 cm−1 for I and −11.53 cm−1 for II) in the dimeric units, with Co…Co and Ni…Ni distances of 4.397 (1) and 4.358 (1) Å, respectively, that are related to double syn–anti carboxylate bridges.