The growth kinetics of nanograins in Co3O4 nanofibers has been investigated. Individual fibers were made up of nanograins. The nanograins were observed to coalesce and grow at the expense of the smaller ones, similar to the phenomenon observed in the sintering process of bulk ceramics. The activation energy and the growth kinetics of nanograins were estimated, showing the dominant growth mechanism of nanograins to be likely related to a lattice diffusion process. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.