Background/aim: Calcineurin, an inhibitor of calcium dependent phosphatase is highly presented in a brain of an Alzheimer’s disease. Aging brain gets more sensitive to hyperactivation of calcineurin, and this event causes tau neurofibrillary plaque accumulation, which is one of the outcomes of this disease. The regions of hippocampus are much effected from the results of this process. Our hypothesis is that a calcineurin inhibitor, tacrolimus, could prevent the accumulation and the decrease of the neuronal cells. Therefore, this immunosuppressive drug could be a candidate for an early treatment of Alzheimer disease. Materials and methods: Fifteen male Wistar albino rats were divided to three groups; control, Alzheimer, and Alzheimer+Tacrolimus. The Alzheimer group received an injection of streptozotocin intracerebroventricularly for the purpose of modelling the disease via generating free radicals leading a cognitive impairment. Alzheimer+Tacrolimus group first received an oral drug, a calcineurin inhibitor for 10 days afterwards prepared for the model as same as the Alzheimer group received. Finally, all groups performed the Morris water maze test for four days then sacrificed. For the aim of counting neurons in the hippocampus stereological methods, as well as for an evaluation of cellular response to stress in dentate gyrus, a c-Fos immunohistochemistry was performed. Results: According to the probe trial of Morris water maze test, the latency time was dramatically higher at both Alzheimer and Alzheimer+Tacrolimus group (p < 0.01). We confirmed these results with our stereology data. The results from stereology technique indicate that there was a neuronal decrease at the hippocampus regions in Alzheimer and Alzheimer+Tacrolimus group. Our outcomes from immunohistochemical data showed a significant increase in the number of c-Fos-positive cells in Alzheimer group when comparing with Alzheimer+Tacrolimus group (p < 0.001). Conclusion: There was none preventive effect for neuronal loss in the hippocampus under the effect of tacrolimus drug according to stereological results. However, tacrolimus administration may have reduced cellular stress and cell damage.