Herein, injectable, non-diffusible, and pre-filled bone pastes are developed using α-tricalcium phosphate (α-TCP) and hydrophobically modified poly(vinyl alcohol) s (hm-PVAs) with various alkyl chain lengths (3-12). The resulting bone pastes show high injectability (over 90%) when the solid-liquid ratio is lower than 3.5. The non-diffusion property of α-TCP/hm-PVAs bone pastes in water and fresh porcine blood is observed compared with α-TCP alone, α-TCP/original PVA (Org-PVA), and commercial calcium phosphate paste. The compressive strength of α-TCP/nonanal-modified PVA (C9-PVA) bone pastes is 5.4 AE 1.4 MPa within 24 h and reaches 27.5 AE 2.7 MPa after 7 days in water. Young's modulus of α-TCP/C9-PVA bone pastes is 0.84 AE 0.02 GPa, which is lower than that of commercial calcium phosphate paste (1.5 AE 0.02 GPa) and poly(methyl methacrylate)-based bone cement (1.06 AE 0.03 GPa). Furthermore, the surface of α-TCP/C9-PVA bone pastes shows excellent cell adhesion of cultured osteoblastic cells. These results demonstrate that α-TCP/C9-PVA bone paste is a promising bone filler for percutaneous vertebroplasty (PVP) surgery.