In this communication, manganese oxide (Mn3O4) nanoparticles were prepared by a facile solution method using starch as capping agent. The nanoparticles were characterized by means of X‐ray diffraction (XRD) and AFM. The results showed that the Mn3O4 nanoparticles were single phase, spherical, and uniformly dispersive. The average particle size was evaluated to be approximately 35 nm.