Thermosensitive composite hydrogels incorporated with particles have been considered as next-generation biomaterials for numerous applications. However, experimental results reported in literature are not yet completely free of controversy with regard to how the particle filler affects the rheological behaviors of the resulting hydrogels. In this study, a simple method was developed to synthesize hydroxyapatite (HA) particles with definable morphology (rod and sheet) using hydrothermal process. The size of HA particles, ranging from 46 to 1149 nm, could be tailored by utilizing a sodium oleate surfactant. These HA particles introduced into thermosensitive hydrogels of poly (ethylene glycol) methyl ether-block-poly (lactide-co-glycolide) to systematically investigate the particle effect on the rheological behaviors of resulting HA-hydrogels. Experimental data confirm the mechanical and rheological behaviors of resulting HA-hydrogels were significantly influenced by particle morphology (size and shape) and the surfactant on the surface of the particle. These results act as solid evidences to highlight the crucial role of particles for developing composite hydrogels with desire thermosensitivity and mechanical properties for use in bioengineering applications. (C) 2014 Elsevier B.V. All rights reserved.