Background and purpose: The COVID epidemic is affecting individuals worldwide, and Alzheimer's disease (AD) and amnesic mild cognitive impairment (MCI) patients are at risk due to their characteristics and age. We analysed the impact of the pandemic on these patients' neuropsychiatric symptoms and their quality of life after five weeks of lockdown in Spain. Methods: We tested 40 subjects with a diagnosis of MCI (20) or mild AD (20) from the Cognitive Stimulation Program of Cognitive Disorders Unit. All patients had undergone a previous evaluation during the month before the lockdown, and they were re-evaluated after 5 weeks of lockdown. The Neuropsychiatric Inventory (NPI) and EuroQol-5D were used to evaluate the neuropsychiatric symptoms and quality of life of patients and caregivers. Results: The total baseline NPI score was 33.75 (22.28) vs 39.05 (27.96) after confinement (p=0.028). The most frequent neuropsychiatric symptoms affected were apathy (4.15 (3.78) vs 5.75 (4.02); p=0.002) and anxiety (3.95 (3.73) vs 5.30 (4.01); p=0.006) in MCI patients and apathy (2.35 (2.70) vs 3.75 (3.78); p=0.036), agitation (0.45 (1.14) vs 1.50 (2.66); p=0.029) and aberrant motor behaviour (1.25 (2.86) vs 2.00 (2.93); p=0.044) in AD patients. We did not observe differences in EuroQol-5D scores during the reevaluation. Approximately 30% of patients and 40% of caregivers reported a worsening of their health status during confinement. Conclusions: We have demonstrated the worsening of neuropsychiatric symptoms in patients with AD and MCI during 5 weeks of lockdown, with agitation, apathy and aberrant motor activity being the most affected symptoms.