Nanocrystalline tantalum-doped chlorapatite(Ta-doped ClA) was successfully synthesized using a facile mechanochemical method. In the absence of the dopant, milling for 3 h led to the formation of a poorly crystalline hydroxyapatite, while in its presence of the Ta dopant, Ta-doped ClA nanopowders were produced as a result of an oncoming reaction. The results indicated that lattice micro-strain, crystallite size, crystallinity level, phase percentage and hexagonal lattice constants of the substituted apatite nanopowders were dramatically affected by the doping concentration. The a-axis and unit cell volume increased with the increase in the doping concentration, owing to the ionic radius difference of Cl~- and OH~- ions. From the TEM observations, the doped powders consisted of nanoneedles with a mean size of 60 ± 20 nm in length and 14 ±4 nm in width. Nanocrystalline tantalum-doped chlorapatite (Ta-doped ClA) was successfully synthesized using a facile mechanochemical method. In the absence of the dopant, milling for 3 h led to the formation of a poorly crystalline hydroxyapatite, while in its presence of the Ta dopant, Ta-doped ClA nanopowders were produced as a result of an oncoming reaction. The results indicated that lattice micro-strain, crystallite size, crystallinity level, phase percentage and hexagonal lattice constants of the substituted apatite nanopowders were dramatically affected by the doping concentration. The a-axis and unit cell volume increased with the increase in the doping concentration, due to the ionic radius difference of Cl ~ - and OH ~ - ions. From the TEM observations, 20 nm in length and 14 ± 4 nm in width.