Sodium acetate trihydrate can be obtained from the crystallization of sodium acetate in water. On heating at 75C it melts while on heating above 120C it loses water of crystallization and gets converted into anhydrous form. The hyperfine proton and 13C splittings have been evaluated by recording ESR spectra of its irradiated single crystals. ESR studies suggested the existence of trapped methyl radicals. Its crystals are monoclinic and its crystal structure has been investigated by photographic methods. Unit cell parameters were evaluated.