trans-Dihydroxo[5,10,15,20-tetrakis(n-pyridyl)porphyrinato]tin(IV) (n = 3 and 4) complexes have been synthesized and fully characterized. X-ray structural analysis of trans-dihydroxo[5,10,15,20-tetrakis(4-pyridyl)porphyrinato]tin(IV) reveals that the supramolecular hydrogen bondings between the hydroxotin(IV) porphyrins and lattice water molecules form a hydrogen-bonded two-dimensional network. The hydrogen bonding mode between the tin(IV) porphyrins and the water molecules closely resembles that of the hydrogenbonded outer-sphere intermediate in the acidolysis of dihydroxotin(IV) porphyrins.