Incidental findings are common in presumed healthy volunteers but are infrequently studied in patients in a clinical context.To determine the prevalence, nature, and management implications of incidental findings on head MRI in patients presenting with cognitive symptoms, and to quantify and describe unexpected MRI abnormalities that are of uncertain relevance to the patient's cognitive symptoms.A single-centre retrospective review of patients attending a regional early-onset cognitive disorders clinic between March 2012 and October 2018. Medical records of consecutive patients who underwent head MRI were reviewed. Unexpected MRI findings were classified according to their severity and likelihood of being incidental. Markers of small vessel disease and cerebral atrophy were excluded.Records of 694 patients were reviewed (median age 60 years, 49.9% female), of whom 514 (74.1%) underwent head MRI. 54% of the patients received a diagnosis of a neurodegenerative disorder. Overall 111 incidental findings were identified in 100 patients of whom 18 patients (3.5%, 95% CI 2.2-5.6%) had 18 incidental findings classified as requiring additional medical evaluation. 82 patients (16%, 95% CI 13.0-19.5%) had 93 incidental findings without clearly defined diagnostic consequences. 17 patients (3.3%) underwent further investigations, 14 patients (2.7%) were referred to another specialist clinic and 3 patients (0.6%) were treated surgically. Two patients had MRI findings of uncertain relevance to their cognitive symptoms, necessitating prolonged clinic follow-up.Incidental findings are common in patients with cognitive impairment from this large clinic-based series; however, few required additional medical evaluation. These data could help inform discussions between clinicians and people with cognitive symptoms regarding the likelihood and potential implications of incidental imaging findings.