Objective: To evaluate the feasibility and effectiveness of a new approach for craniofacial augmentation by a minimally-invasive subpericranial injection. Three commercially available semi-liquid bioceramic bone-grafting materials were examined for this application in a rat model. Material and Methods: Twenty-four adult male rats were randomly assigned to undergo onlay calvarial grafting by subpericranial injection of three semi-liquid bone void fillers: Norian SRS(calcium phosphate), ChronOs Inject^TM (porous beta-tricalcium phosphate), or BonePlastharvested after 24 hours to serve as controls. The rest were studied after 16 weeks. The volume fraction of the following parameters was morphometrically measured: new bone, blood vessels, residual bone filler and inflammation. Results: In all study groups (including controls), histological examination demonstrated that bone fillers were successfully delivered to the desired subpericranial space by the percutaneous injection method. New bone formation was evidenced adjacent to the cranial bone in all the study groups. The Norian filler material survived in a significantly higher volume fraction (38.4% ± 6.5%) than the ChronOs filler (18.8% ± 1.6%; P < 0.0001) and the BonePlast filler (17.8% ± 1.5%; P < 0.0001). New bone was formed in all groups, particularly adjacent to the interface of graft material with native bone but only to minimal extent. Conclusion: This new approach for craniomaxillofacial augmentation was successfully demonstrated in a rat model. The Norian filler (calcium phosphate) demonstrated superior space preservation abilities. This model may be further applied to test new injectable bone substitutes in the craniomaxillofacial area.