In this study, the effects of different sintering temperatures (900-1300oC) and the addition of different amounts of magnesium oxide (0.5%, 1% and 2% by weight) to microstructural, physical and mechanical properties of a commercial purity hydroxyapatite were examined. Although the physical properties of hydroxyapatite without magnesium oxide increased with increasing sintering temperature, the compressive strength and fracture toughness properties decreased at temperatures above 1100oC due to three main reasons (decomposition, excessive grain growth and microcrack formation). While the main phase for all samples was hydroxyapatite; beta/alpha-tricalcium phosphate and calcium oxide in hydroxyapatite, and whitlockite in magnesium oxide added hydroxyapatites were detected as trace phase. It was determined that the average grain size of magnesium oxide added hydroxyapatites for all temperatures was lower than that of pure hydroxyapatite. However,  the microstructures of 1% by weight of magnesium oxide HA are composed of more homogeneous and uniformly grains. The addition of magnesium oxide to hydroxyapatite in the ratio of 0.5% and 1% was found to contribute to the increase of physical and mechanical properties of pure hydroxyapatite at all temperatures. Due to its porous structure, 2% magnesium oxide added hydroxyapatite had lower sinterability than others. The 1% magnesium oxide added hydroxyapatite has 38% more resistant to compression strength (183.25±25.09 MPa) and has 53% more fracture toughness (1.472±0.041 MPam1/2)  than pure HA, but is not suitable for use in the human body due to its low fracture toughness.