In the present study, a hydrothermal hot pressing (HHP) method was used to fabricate porous hydroxyapatites with high strength. In particular, an interconnected matrix of hydroxyapatite was achieved by solution precipitation and the application of compressive stress during HHP. Hydroxyapatite samples post-sintered after this HHP treatment had a lower relative density and higher open porosity than those prepared by normal sintering. An examination of the pore characteristics suggested that the samples after HHP treatment and post-sintering had a high amount of open pores with a large and round morphology, whereas the samples prepared by normal sintering showed a denser microstructure, with a sharp-edged-pore morphology.