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Importance Socioeconomic deprivation is associated with increased risk of co-morbid diseases that are modifiable risk factors for dementia. Deprivation is also associated with reductions in hippocampal and amygdala volume, key regions in neurodegenerative pathology. To date, these changes have not been studied in real world populations of cognitive impairment. Machine learning approaches have now allowed visualisation of smaller structures such as hippocampal subfields from routine clinical MRIs when previously not possible.Objective To investigate the association between socioeconomic deprivation, and apriori selected volumes (whole brain, hippocampus, hippocampal subfields, amygdala) in patients with cognitive impairment.Methods Patients from South London and Maudsley (SLaM) Image Bank diagnosed with MCI or dementia subtypes with an available MRI scan were identified. UK Index of Multiple Deprivation (IMD) scores, modifiable dementia risk factors (hypertension, diabetes, cerebrovascular accident and asthma) were obtained. Multiple linear regression models adjusted for age, gender, ethnicity, and modifiable risk factors were compared with hippocampal subfields, whole hippocampus and amygdala (ANTsX pipeline – Deepflash with the DSK atlas applied, corrected for total intracranial volume) with stratified analyses for cognitive impairment subtypes.Results 3,075 patients (mean age 77, 58% female, 40% minoritized ethnicity, AD (n=2003), MCI (n=660), VaD (n=239), other/unspecified (n=173) were included in this retrospective cohort study. Higher IMD (more deprived) were associated with significantly reduced hippocampal and amygdala volumes across all cognitive impairment types. For every 10-point increase in IMD (greater deprivation), hippocampal volume decreased by 76 ml (left) (p=0.002) and 104 ml (right) (p<0.001), CA1 subfield volume decreased by 46 ml (left) (p<0.001) and 43 ml (right) (p=0.001), parahippocampal gyrus volume decreased by 58 ml (left) (p=0.011) and 51 ml (right) (p=0.034) and perirhinal cortex volume decreased by 37 ml (left) (p=0.046) and 44 ml (right) (p= 0.001), and amygdala volume decreased by 12 ml (left) (p=0.004) and 14 ml (right) (p<0.001). The strongest associations were observed between higher IMD and reduced hippocampal and subfield volumes were in the AD and MCI groups.Conclusion We show higher deprivation is associated with distinct hippocampal subfield and amygdala volume atrophy in cognitively impaired individuals. Socioeconomic deprivation may have a larger role in reflecting regional vulnerability to neurodegeneration than previously thought.