Aim To verify the prevalence and presence of frailty markers, and their relationship to cognitive function among older adults with amnestic mild cognitive impairment (aMCI). Methods This was an observational study with transversal analyses. Older adults with aMCI as a result of Alzheimer's disease (n = 40) were compared with healthy controls (n = 26) at the Psychogeriatric Outpatient Unit, Institute and Department of Psychiatry, Faculty of Medicine of the University of São Paulo. All participants were submitted to a broad clinical and neuropsychological evaluation. Frailty was evaluated according to the Cardiovascular Health Study (CHS) phenotype and the Edmonton Frail Scale (EFS). MCI was diagnosed by a multidisciplinary consensus according to the Petersen criteria and cerebrospinal fluid analysis for Alzheimer's disease biomarkers. Results The prevalence of frailty was significantly higher in the aMCI compared with the control group when it was assessed with the EFS (P = 0.047), but not with the CHS (P = 0.255). The prevalence of frailty varied on the criteria used (EFS 7.5%; CHS 30%). The fatigue variable in the CHS (P = 0.036), and the mood (P = 0.019) and functional independence (P = 0.042) variables from the EFS were significantly different between the groups. Visuospatial function (OR 2.405, P = 0.042) was associated with the CHS criteria. Conclusion The identification of frailty features in aMCI appears to depend on the protocol used for evaluation. Visuospatial function showed a higher risk for frailty with the CHS. Geriatr Gerontol Int ••; ••: ••–••