Aims: To examine the rates and clinical characteristics of mild cognitive impairment (MCI) in older people with depressive symptoms and to determine the relative contribution of hippocampal volume and MCI to memory change. Method: One hundred and fifty-two participants with lifetime Major Depression and remitted or mild symptoms and 28 healthy controls underwent psychiatric and neuropsychological assessments. Magnetic resonance imaging was also conducted in a subset of the patients (n = 81) and healthy controls (n = 18). Results: MCI was diagnosed in 75.7% of the patients and was associated with increasing age, medical burden, vascular risk factors, later age of depression onset and smaller hippocampi. Multiple regression showed that both hippocampal volume and MCI diagnosis mediate memory performance in depression. Conclusions: MCI occurs in older adults with a history of depression and is not simply due to symptom severity. Memory change is linked to underlying hippocampal atrophy in this patient group.