The added value of neurofilament light chain (NfL) to the existing diagnostic methods is unknown, although a plethora of studies have shown increased levels in cerebrospinal fluid (CSF) and blood in many neurodegenerative and neurological disorders. The added value of CSF NfL was determined in a mixed memory clinic cohort of consecutive patients for 136 patients with Alzheimer's disease (AD) (n = 69), mild cognitive impairment (n = 24), non-AD (n = 34), and also healthy controls (n = 9). This study found no increase in the diagnostic accuracy of the etiological diagnoses but knowing the CSF NfL value led to increased diagnostic certainty for the specialist in neurology.