In this study, we report the synthesis of nickel (Ni) encapsulated manganese ferrite (MnFe2O4) core-particles via ionic interaction. The thickness of Ni shell was optimized by controlling pH, reaction time, and concentration of Ni precursor solutions. Ni ions were encapsulated onto negatively-charged MnFe2O4 core particles at pH > 8. Optimum Ni encapsulation was found to occur at pH of 10, reaction time of 10 min, and concentration of 0.12 M aqueous soultion of Ni. High resolution transmission electron microscopy, energy dispersive spectroscopy, and magnetic force microscopy were used to confirm the phase and structure of the Ni-encapsulated MnFe2O4 particles.