Three-dimensional printed Ti-6Al-4V hemipelvic prosthesis has become a current popular method for pelvic defect reconstruction. This paper presents a novel biomimetic hemipelvic prosthesis design that utilises patient-specific anatomical data in conjunction with the Voronoi diagram algorithm. Unlike traditional design methods that rely on fixed, homogeneous unit cell, the Voronoi diagram enables to create imitation of trabecular structure (ITS). The proposed approach was conducted for six patients. The entire contour of the customised prosthesis matched well with the residual bone. The porosity and pore size of the ITS were evaluated. The distribution of the pore size ranged from 500 to 1400 μm. Porosity calculations indicated the average porosity was 63.13 ± 0.30%. Cubic ITS samples were fabricated for micrograph and mechanical analysis. Scanning electron microscopy images of the ITS samples exhibited rough surface morphology without obvious defects. The Young's modulus and compressive strength were 1.68 ± 0.05 GPa and 174 ± 8 MPa, respectively. Post-operative X-rays confirmed proper matching of the customised prostheses with the bone defect. Tomosynthesis-Shimadzu metal artifact reduction technology images indicated close contact between the implant and host bone, alongside favourable bone density and absence of resorption or osteolysis around the implant. At the last follow-up, the average Musculoskeletal Tumour Society score was 23.2 (range, 21-26). By leveraging additive manufacturing and Voronoi diagram algorithm, customised implants tailored to individual patient anatomy can be fabricated, offering wide distribution of the pore size, reasonable mechanical properties, favourable osseointegration, and satisfactory function.