Hydroxyapatite (HA) synthesized with the hydrothermal method was studied under various preparation conditions including variations of time, concentration of reactants, and concentration of surfactant, Aminotris (methylenephosphonic acid) [N(CH₂PO₃H₂)₃] (ATMP).  Well elongated crystals with high degree of crystallinity were synthesized at 150 ^oC, initial pH adjusted to 9.0 ± 0.1 with no surfactant and a high concentration of reactants. Addition of the surfactant helped in increasing particle agglomeration and formation of clusters of micron sizes. HA crystal sizes were ranged from 1.4 µm to 5.1 µm whereas the crystallite sizes ranged from 26 nm to 38 nm. The antiviral screening of the hydroxyapatite was performed against Viruses that represent a threat to the public health community due to their minimal symptomatic control such as HAV, HSV-1, Adenovirus, and MERS. The antiviral activities of the synthesized compound were evaluated In vitro by viral infectivity Plaque assay. The obtained results revealed that the synthesized Hydroxyapatite - using 0.075 M CaHPO₄ concentration for 25 hours hydrothermal time with 100 ppm surfactant - exhibited antiviral effect (52.9 %) against Virus HSV-1. HAV was slightly inhibited, whereas no antiviral activity was observed with respect to Adenovirus-5, and MERS.