Alzheimer’s disease (AD) is a multifactorial brain disorder and infectious diseases are considered as one of the predisposing factors for AD. Toxoplasma gondii, an obligate intracellular parasitic protozoan, is suspected of being associated with AD. Serum samples were collected from 109 AD patients and 114 age-matched healthy controls. ELISA was performed using recombinant T. gondii cyst wall protein 1 (CST1) to detect T. gondii antibodies. A parallel experiment was performed with Toxoplasma gondii tachyzoites lysate protein. To analyze whether factors associated with the onset of AD included chronic T. gondii infection, a multivariate logistic regression model was applied, further validating the correlation between chronic T. gondii infection and AD. AD patients exhibited significantly higher levels of Toxoplasma-specific antibodies in their serum compared to the control group, with statistically significant differences (p < 0.05). Multivariate logistic regression analysis revealed that Toxoplasma infection is a risk factor for AD (p < 0.01), and the CST1 antigen can significantly improve the model’s performance in predicting the occurrence of AD. The results indicate that chronic infection with Toxoplasma gondii could be one of the risk factors for the development of AD, potentially predisposing individuals with underlying health conditions to the disease. This further validates the correlation between Toxoplasma gondii and AD.