Alzheimer’s disease (AD) is the most seen form of neurodegenerative disease with specific pathological findings like; senile plaques (CPs), synaptic loss, neurofibrillary tangles (NFTs) and neurodegeneration. Homocysteine is a naturally occurring amino acid and have a role on the body’s methylation process. In this study, total 12 rats, were used and divided into 2 groups. Group 1 Control group (n = 6): No rats were treated. Group 2 Application of High-Dose Homocysteine (n = 6): For 5 weeks, 4 mg / kg / day; to create an experimental Alzheimer model. Morris Water Maze test, the MDA, homocysteine (Hcy), reduced glutathione (GSH) and oxidised glutathione (GSSG) levels in rat liver, serum and erythrocyte samples were studied. Mitogen activated protein kinase (MAPK) and beta-secretase (BACE1) mRNA levels and pathological examinations were performed in rat hippocampus samples. The reaching time to exit platform was longer in the Hcy group according to Morris Water Maze test. Neurodegenerative areas were observed in the hippocampus CA1 region of Hcy group. Liver and serum Hcy and MDA levels and liver and erythrocyte GSSG levels were significantly higher (p <0.01) while GSH levels were lower in the liver and erythrocyte samples compared to control (p <0.01). MAPK and BACE1 mRNA levels of the hippocampus were significantly higher in the Hcy group (p <0.01). Different studies results indicate that; increased plasma homocysteine level was found to be a strongly independent risk factor for the progress of dementia and Alzheimer’s disease. However, there is also contradictory evidence, and it is still controversial whether HHcy is a risk factor for AD or just a bio producer. This study was carried out to determine homocystein role in Alzheimer process. According to findings It is very important to keep homocyteine level in lower grade to reduce or eliminate AD possibility.