Repair and regeneration of tissue engineering in different organs, including bone defects is important. Bone tissue engineering, develops structures that follow from natural bone environment to provide biological responses in order to regenerate bone defects. According to nanocomposite fibrous structure of bone, synthesis of polymer matrix scaffold that filled with ceramic as filler can be effective. Electrospinning is an effective method to synthesis of fibrous scaffolds that they are similar to extra cellular matrix. In this research, we prepared diopside nanopowder by sol-gel method and XRD pattern of powder showed good agreement with the standard card of diopside (JCDP:00-019-0239) confirming the synthesize of pure diopside powder without any second phase. According to Modified Scherrer Equation , the crystallite size of diopside powder was in the range of 32 nm. TEM image also confirmed that diopside nanopowder had uniform particles with width distribution (53.63 ± 26 nm). In the following, we developed polycaprolactone-diopside nanocomposite fibrous scaffold with difference diopside contents. In order to distinguish the optimum fibrous scaffold, fibers morphology, mechanical properties, degradation rate and bioactivity were evaluated. Due to the low hydrophilicity of synthetic polymers, the optimum scaffold of polycaprolactoe-diopside was modified by using gelatin. In the following, the effects of this structure on the scaffold morphology, physical properties, growth and cell adhesion was evaluated. The results showed, average fiber size was reduced from 260 ± 74.7 to 816.81 ± 101.5 depending on the diopside content. Furthermore, diopside nanoparticle could significantly improve hydrophilicity, bioactivity. In fibrous polycaprolactone-3 wt. % diopside scaffold, ultimate tensile strength enhanced from 0.6 ± 0.1 MPa to 4.9 ± 0.1 MPa, strain at break enhanced from 33.9 ± 7.5 % to 101.0 ± 4.0 % and Tensile modulus enhanced from 5.3 ± 0.9 MPa to 9.8 ± 0.35 MPa that was selected as Optimized scaffold. Due to the agglomeration of nanoparticles at high diopside content, mechanical properties were decreased. Surface modification of polycaprolactone-diopside scaffold by using gelatin, after swelling in water/acetone for 20 min leaded to decrease water contact angle and from 109.4 ± 0.5 degree to 65.9 ± 1.6 degree and increased cell adhesion. So, polycaprolactone- 3 wt. % diopside-gelatin nanocomposite fibrous scaffold with controllable mechanical and biological properties, can be suitable in order to repair of bone defects. Keywords: Bone Tissue Engineering, Electrospinning, Polycaprolactone, Diopside nanoparticles, Gelatin.