We report on the magnetic properties of multiferroic hexagonal HoMnO 3 single crystals and polycrystalline samples with micrometer and nanometer particle size. We have studied the in-plane and out-of-plane magnetization of HoMnO 3 single crystals under low applied magnetic fields in the temperature range below T Néel= 72 K and observe the bifurcation of zero-field-cooled and field-cooled curves at the Mn spin reorientation transition temperature at 34 K. In addition, the c-axis magnetization shows a ferrimagnetic-like behavior which may relate to the magnetic Ho 3+ and Mn 3+ domain boundary structures and sensitively respond to changes of the magnetic structure such as spin rotations at the phase transitions near 5 and 34 K. We also studied the particles' size dependent magnetic behavior in the HoMnO 3 polycrystalline samples and observe the presence of a net magnetic moment at the surface due to the large surface/volume ratio. Below the Ho 3+ ordering temperature of 5 K, magnetization curves as a function of applied magnetic field, in contrast to those for the single crystal, show hysteresis behavior with coercivity, which increases with diminishing particle size.