Wet milling followed by heat treatment was used to synthesize single-phase nanocrystalline BaFe12O19 powders with mean crystallite size of about 50 nm. In order to understand the effect of mean crystallite size on structural and magnetic properties, calcined samples were dry milled for 2 and 4 h. TEM images and XRD measurements showed that by dry milling the mean crystallite size changed. However, some amorphous areas were also presented within the structure. It was also observed from the magnetic measurements that with the increase of the dry milling time, saturation magnetization decreased from 61 emu/g to 10 emu/g. The coercivity also decreased from 4800 Oe to 350 Oe due to the decrease in the mean crystallite size and the formation of amorphous areas. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.