for the densification of ceramics in its original phase at very low temperatures <300^°C using pressure (<500 MPa) and transient liquid. Densifying the nano-hydroxyapatite in their original form for bone regeneration applications is viable in CSP and the densification relies upon the factors like powder source, processing parameters (temperature, pressure and hold time) and transient liquid (aqueous, acid and base). Our present investigation is about the densification of commercial nano HA of two different agglomerate sizes processed via wet chemical precipitation and spray drying. The spherical morphology, phase purity and particle size are confirmed by scanning electron microscopy, X-ray diffraction and particle size measurement techniques. The cold sintering of HA was carried out using acetic acid, and phosphoric acid (10 wt. %) under a moderate pressure of 360 MPa at 200^°C. Also, the effectiveness of water in the cold sintering of commercial HA has been tested under the same experimental conditions for comparison. With respect to the acid concentrations (0.5 M, 1.0 M, 2.0 M, & 3.0 M) under the same operating pressure and temperature, the relative densities are varied linearly and a maximum of 92% densification has been achieved for the experiment carried out with 3.0 M phosphoric acid. Meanwhile, water has not considerably aided the HA densification compared to acid solutions. Overall, the results demonstrate the importance of the nature of the transient liquid, its concentration, and particle size in the cold sintering of HA powders for biomedical applications.