Objective: The aim of this study was to evaluate bone regeneration histologically after topical application of Strontium Ranelate gel in critical size bone defects in the tibia of induced diabetic rats. Subjects and methods: sixty adult male albino rats were used in this study and divided into four groups equally, fifteen rats for each group. These groups were Normal control group (N), Diabetic control group (D), Normal experimental group treated with SrR gel (NSR) and Diabetic experimental group treated with SrR gel (DSR). Five animals from each group were sacrificed at 5, 10 and 30 days alternatively postoperatively. After termination of the experiment, the specimens were prepared and bone formation was evaluated histologically by H&E stain and Masson's trichrome stain. Results: In experimental groups treated with SrR, there was acceleration in the formation and mineralization of granulation tissue and woven bone, also there was acceleration in the conversion of woven bone to spongy bone. While in Diabetic control group there was obvious retardation in formation and mineralization of granulation tissue and bone than all other groups. Conclusion: The study showed that the topical application of SrR gel can accelerate formation and maturation of granulation tissue. Also, it accelerates bone formation and mineralization in diabetic rats treated with SrR gel.