Purpose: It remains unclear whether estrogen deficiency affects the ultrastructure and tissue-level mechanical properties of the maxilla. The hypothesis of this study was that the ovariectomized rat could induce tissue-level changes of the maxilla. Materials and Methods: Twelve 3-month-old female Sprague Dawley rats were acquired and randomly divided into two groups: ovariectomized and SHAM (control) (n = 6 for each group). Three months after the ovariectomy, implants were placed; the animals were sacrificed at day 28, and then samples were collected and prepared according to the previously established protocols. Advanced analytical equipment including scanning electron microscope with energy-dispersive spectrometry, transmission electron microscope, and nanoindentation were used to analyze bone quality. Results: The results showed that the mature bone areas in the ovariectomized group were significantly affected in the mineral crystal and the microstructure. The micromechanical properties of the mature bone were also affected, showing significantly increased hardness (H) and reduced modulus (Er) in ovariectomized rats compared with the normal rats (P .05). Differences in H and Er in new bone areas between the normal and ovariectomized rats were less significant. Conclusion: Ovariectomy affected maxilla bone tissue-level quality; however, the effects mainly existed in the mature bone areas, which were characterized by higher crystalline mineralization, hardness, and modulus. Keywords: bone, maxilla, nanoindentation, osteoporosis, ovariectomy