Objective In dialysis-dependent and severe chronic kidney disease (CKD) patients, cognitive impairment is found in 16-29%. In community-dwelling population without dementia mixed results have been observed. We investigated the relationship between renal function and cognition in patients from a memory clinic. Methods We performed a cross-sectional study of consecutive patients from a memory clinic between 2005 and 2009. Renal function was estimated with the Modification of Diet in Renal Diseases (MDRD) and Cockcroft-Gault (CG) formulas, and categorized into ordinal groups: reference ≥60-ml/min/1.73-m2, mild CKD 45-59-ml/min/1.73-m2 and moderate CKD <45-ml/min/1.73-m2. Cognitive function was dichotomized (Mini-Mental State Examination (MMSE) ≥24 vs. <24). We performed multiple logistic regression analyses with adjustment for potential confounders. Results The cohort comprised 581 patients (mean age 77-±-10-years). With the MDRD, there were 74 (12%) cases with moderate CKD and 108 (18%) with mild CKD. With the CG, these prevalences were 144 (30%) and 130 (27%). In mild CKD patients, a significant relationship was found between cognitive function and CKD according to the MDRD-formula [adjusted OR 2.10; 95%CI 1.09-4.05]. In moderate CKD patients, no significant adjusted associations were found. In patients without dementia, significant adjusted associations were found between CKD and MMSE (MDRD: mild CKD [OR 5.09; 95%CI 1.17-22.14] and moderate CKD [OR 5.03; 95%CI 1.10-22.98]; CG: mild CKD [OR 6.16; 95%CI 1.17-32.50] and moderate CKD [OR 5.60; 95%CI 1.01-30.91]). Conclusion This study showed a significant association between mild CKD and impaired cognitive function in patients from a memory clinic, especially in patients without dementia.