Zirconium oxide fiber was prepared by electrospinning technique and sol-gel processing from zirconium acetate and poly(methyl methacryate) (PMMA) as precursor. Calcination of these structures between temperature of 450 and 1000 degrees C resulted in the formation of zirconium oxide fiber whose diameters ranged from 1000 to 500 nm. The samples of calcination at 450 and 500 degrees C were observed of only in the tetragonal phase. The tetragonal phase and monoclinic mixed phase appeared between 600 and 900 degrees C. After calcination at 1000 degrees C, only the monoclinic phase was identified in the XRD patterns. Grain size increased with increasing calcinations temperature. Pure monoclinic phase with grain size of 25.70 nm was obtained from the calcination temperature of 1000 degrees C. The activation energy for grain growth of electrospun zirconium oxide fiber was estimated to be 20.48 kJ/mol. (C) 2012 The Ceramic Society of Japan. All rights reserved.