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Aim In this study, the relationship between kidney function, cognitive performance, functional abilities and mood was investigated in a community-dwelling Italian oldest-old population. Methods Serum creatinine was used to calculate estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease formula, for 415 oldest-old without dementia participating in the 'Health and Anemia' study, a prospective, observational cohort study. The cross-sectional associations of kidney function with cognitive performance on several neuropsychological tests, basic and instrumental functional abilities and mood were analyzed using univariate and multivariable linear regression models. Results Cognitive performance and functional ability significantly worsened with decreasing kidney function. After adjusting for age, sex, education, comorbidity index of the Cumulative Illness Rating Scale (CIRS), body mass index, bone fracture and serum ferritin levels the associations of eGFR categories with basic and instrumental functional abilities continued to be statistically significant whereas that with global cognitive functions did not. No significant independent association was found between renal function and mood. Conclusions Oldest-old with reduced kidney function showed greater basic and instrumental functional disabilities, while cognitive function, although decreased with decreasing eGFR, was no longer significantly associated with eGFR categories after adjusting for confounders.