Introduction. In the field of orthopaedic surgery, the use of osteogenic material in larger defects is essential. Autograft and allograft are both known methods, and autograft is believed to be the best choice. But autograft is associated with additional invasive procedures which can prove difficult in fragile patients and can cause local side effect after bone harvest. For feasible purposes, the use of allograft is hereby rising and comparing efficacies, and the differences between autograft and allograft are essential for the clinical outcome for the patients. Method. 24 female Norwegian brown rats were included, 12 normal rats and 12 induced with osteoporosis (OP). OP inducement was verified in vivo by bone volume fraction (BV/TV) at 90 days after ovariectomy (OVX). The primary surgery in each rat consisted of a 2:5 × 3 mm hole in the proximal tibia, bilaterally. Autograft and allograft were randomly allocated in the right and left tibia. After an observation of 21 days, the rats were sacrificed. Tibia samples were harvested, micro-CT scanned for bone inducement and microarchitectural properties, and then embedded for histology. Results. The OP induction was verified three months after the OVX by a reduction of 68.5% in the trabecular bone BV/TV compared to normal bone. Microarchitectural analysis and histology showed no significant differences in the bone-forming capabilities between autograft and allograft in normal or osteoporotic bone after 3 weeks. Conclusion. This study did not demonstrate any difference between autograft and allograft in a normal or osteoporotic rat tibial defect model after 21 days, suggesting allograft is a good alternative to autograft.