This thesis presents an automatic system for cognitive impairment detection from facial expressions in people with mild cognitive impairment and dementia. Dementia is one of the main causes of disability and dependency in the elderly worldwide, leading to impairment in cognitive functions, and its global prevalence is a pressing concern for national health-care systems. Currently, there are no approved disease-modifying therapies. Early detection is thus crucial for the well-being of patients and their caregivers, and to enable patients’ inclusion in research and clinical trials for therapies in development. A precursor stage of dementia known as mild cognitive impairment (MCI) has been identified, in which daily activities are still not greatly affected.