Background: The concept of ‘cognitive frailty’ (CF) was first developed by an international consensus group in 2013 and defined as evidence of both physical frailty and cognitive impairment without a clinical diagnosis of AD or another dementia. CF has been associated with adverse health outcomes and early identification is vital. Difficulty in the assessment of CF however is the lack of a diagnostic gold standard. Objectives: This review aimed to identify assessment tools used to diagnose cognitive impairment in the diagnosis of cognitive frailty, their psychometric qualities and clinical utility. Research design and methods: Six databases were searched between 2013–2024. Studies were eligible if they reported a method of defining cognitive frailty, named the assessment tools, and stated cutoff values used to define cognitive impairment. Results: In the 116 included studies, large heterogeneity was found in the tools utilised, and cutoff scores applied, to diagnose cognitive impairment in the diagnosis of cognitive frailty. This review has demonstrated that diagnosis of CF relies predominantly on the use of three cognitive assessment tools (Mini Mental State Examination, Montreal Cognitive Assessment, Clinical Dementia Rating) from a total of 22 different tools identified in the literature. For assessment of physical frailty, 11 different tools were identified, with the Fried Frailty Index and FRAIL Scale predominantly utilised. Discussion and Implications: The variation in the tools used to identify the diagnosis of CF means there is inconsistency in reporting, potentially impacting both the understanding of the prevalence, and the appropriate direction of intervention strategies.