Sulfamerazine is one of the active members of antibacterial sulfonamides family. Transition metal Co(II) complex of sulfamerazine was synthesized by using Reflux method. The title compound, Co(C11H12N4O2S)2(C5H5N)2] H2O has been studied by method of X-ray crystallography and crystallizes in monoclinic space group C2/c with Z=8. The molecular structure is stabilized by intramolecular and intermolecular interactions. The ORTEP & PLATON view of the title molecule indicating atomic numbering scheme with thermal ellipsoids are drawn at 50% probability level are shown in this book.