Formation of ZrB 2 by volume combustion synthesis (VCS) and mechanochemical process (MCP) from ZrO 2–Mg–B 2O 3 was studied. Production of ZrB 2 by VCS in air occurred with the formation of side products, Zr 2ON 2 and Mg 3B 2O 6 in addition to MgO and ZrB 2. Zr 2ON 2 formation was prevented by conducting VCS experiments under argon. Wet ball milling was applied to the VCS products before leaching for easier removal of Mg 3B 2O 6 phase. MgO and Mg 3B 2O 6 were removed from wet ball-milled products by leaching in 5 M HCl for 2.5 h. In MCP, 30-hour ball milling was found to be sufficient for the formation of ZrB 2 with no minor phase formation. Leaching of MCP products in 1 M HCl for 30 min was sufficient to remove MgO. Complete conversion of ZrO 2 to ZrB 2 did not take place in both production methods, even with excess amounts of Mg and B 2O 3. Therefore, formed ZrB 2 contained residual ZrO 2.