Introduction and objective: It was aimed to examine the relationship between cognitive impairment (CI) and Aβ40, 42, Aβ42/40 ratio and p-tau181 in chronic kidney disease (CKD) patients at all stages. Patients: The patients were divided into four groups; control, the early stage CKD (stage 1–3), the advanced stage CKD (stage 4–5) and the hemodialysis group. All patients completed the MMSE and MoCA tests for CI. The Aβ40, Aβ42, p-tau181 levels of all participants were measured. Result: The result of the MMSE was significantly lower in CKD group (p = 0.005). There was a significant negative correlation between the MMSE and CKD stages (Spearman's rho = −0.29, p = 0.001). The Aβ42 level was significantly lower in the hemodialysis patients. The highest Aβ40 level was observed in the hemodialysis patients, and the Aβ40 level was significantly higher in the advanced CKD group as compared to the early CKD patients and controls (p < 0.001). The Aβ42/40 ratio was low in the hemodialysis patients (p = 0.001). There was a significant negative correlation between the MMSE and Aβ40 (Spearman's rho = 0.18, p = .018), and a positive correlation between the MMSE and the Aβ42/40 ratio (Spearman's rho = −0.360, p < .001). MoCA was negatively correlated with the Aβ40 levels (Spearman's rho = −0.185, p = .019). In the multiple analysis with the MMSE, it was determined high Aβ40 level was correlated with the low MMSE score. Conclusion: It was found that there was a significant relationship between CI and the Aβ40 level in the CKD patients, that CI increased as the CKD stages progressed, that there was a significant negative correlation between the MMSE and MoCA tests and Aβ40, and there was a significant positive correlation between the MMSE and the Aβ42/Aβ40 ratio.