We present the results of controlled synthesis of spherical shape magnesium ferrite (MgFe2O4) dense nanoparticles by using ultrasonic spray pyrolysis (USP) method without any post-annealing processes. A new strategy was proposed to improve nano-crystallinity and observed morphology by ethanol (EtOH) addition in the initial precursor solution of MgFe2O4. Influence of EtOH, not only decrease the synthesized secondary particle size but also enhancing crystallization into MgFe2O4 single phase cubic structure. We observe that average nanosphere size decrease from 220 to 189 nm but increases of crystallite size from 9.6 to 19.2 nm with increasing the amount of EtOH from 0 to 20 vol%. Also, surface morphology revealed that nanospheres with some irregular shape and rough surface appear in case of EtOH additives. The magnetic properties are studied and different parameters viz. saturation magnetization, remanence, and coercivity have been correlated with crystallite size. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.