Objectives: To evaluate bone healing after grafting critical-sized calvarial defects (CSD) in rats with strontium-loaded deproteinized bovine bone (DBB). Methods: One circular full-thickness bone defect (Ø 5mm) was prepared on each parietal bone of 42 female wistar rats. One of the defects was left empty as negative control and the other was grafted with either: 1) DBB loaded with 140Μm of Sr per gr biomaterial (DBB/Sr1); or 2) DBB loaded with 700Μm of Sr per gr biomaterial (Group DBB/Sr2); or 3) DBB soaked with sterile saline (DBB/NaCl), to achieve 3 equally-sized groups. Groups of 7 animals were sacrificed after 15 and 60 days post-surgery. Analyses included microCT evaluation of residual defect length and %mineralized tissue and histomorphometric evaluation of %bone, %DBB, and %other tissues within the defect. Differences among the 3 treatment groups were evaluated with One-way Anova and post-hoc Tukey test, while differences between grafted and non-grafted defect within each group were evaluated with the paired t-test; the level of significance was set at P < 005. Results: At 15 days of healing, newly formed bone was in general limited in both grafted and non-grafted defects, irrespective treatment group; DBB/Sr2 presented shorter residual defect length (p<0.05) and larger %mineralized tissue within the defect (p<0.01) compared to the DBB/NaCl group. At 60 days, DBB/Sr2 presented shorter residual defect length and larger %mineralized tissue within the defect than the DBB-Sr1 (p<0.001 and <0.001, respectively) or the DBB/NaCl (p<0.05 and <0.001, respectively) group. Further, DBB/Sr grafted defects showed statistically significant larger %bone (DBB/Sr2: 8.7±0.9, DBB/Sr1: 8.3±1.1; p<0.05) comparing to DBB/NaCl grafted defects (6.9±0.6). %DBB was similar among groups at all experimental periods. DBB grafted defects presented consistently with lower %bone than empty controls (range: 6.9 – 8.7% versus 14.0 – 20.2%, respectively), irrespective treatment group or observation period (p < 0.001). Conclusions: Strontium-loaded DBB grafting in rat calvarial critical-sized defects enhanced bone formation comparing to grafting with DBB/NaCl.