The title complex of [Ni-2(mu-Sal)(4)(Dena)(2)]H2O, [(mu-tetrakissalicylato-kappa-O,O)(bis-N,N- diethylnicotinamide-kappa-N)(binickel(II))] hydrate, C48H52Ni2N4O16, has been synthesized and explained as structure using some elemental analyses. FT-IR spectra, UV- Vis reflectance, magnetic measurements, thermal analysis and x-ray diffraction methods. The results showed that the unit cell of complex includes two molecules Ni-II cation, four molecules salicylates as bridge and two molecules N,N-diethylnicotinamide ligands, also there is one molecule hydrated aqua. The compound crystallizes in the monoclinic space group P2(1)/c with the following unit-cell parameters: a = 13.6776( 6) angstrom, b = 10.5238( 3) angstrom, c = 21.8165( 9), alpha = 90.00 degrees, beta = 126.546( 3)degrees, gamma = 90.00 degrees and Z = 2. The compound [Ni-2(mu-Sal)(4)(Dena)(2)]H2O is a typical paddle-wheel complex structure. Two Ni-II ions are bridged by four salicylate ligands (O2, O2(i), O3, O3(i), O5, O5(i), O6 and O6(i)) using a mu-COO- coordination mode [symmetry code: (i) 1-x, 1-y, 1-z]. Each Ni-II also coordinates to one nitrogen atom (N1 and N1(i)) from one N,N-diethylnicotinamide ligand molecule in the axial position. The complex has strong paramagnetic properties.