It is debated whether non-affected relatives of patients with affective disorders share a specific brain structure endophenotype. Aim of this work is to explore the medial temporal morphology in affected and non-affected members of a family with mood disorders. Hippocampi and amygdalae were manually traced from the 3D magnetic resonance imaging of five affected family members, 10 non-affected relatives, and 15 unrelated matched controls. Affected and non-affected relatives were characterized by larger left amygdalae (18%, p=0.030), smaller right hippocampus (up to 18%, p<0.0005), and reduced hippocampal asymmetry (p<0.001) than controls. Abnormal, albeit non significant, positive correlations of MTL volumes with age were observed, with the exception of smaller volume of the left hippocampus with advancing age (r=-0.76) in the affected relatives. These data add to the evidence that abnormal medial temporal structures may constitute an endophenotype for affective disorders.