Maternal mental disorders can significantly impact on children's psychosocial and psychological development, incurring substantial ongoing economic and personal costs. A key mediating mechanism is mother–infant relationship quality (MIRQ). Research studies and perinatal mental health screening initiatives have predominantly focused on depressive symptoms and perinatal depression as predictors of MIRQ. While maternal depression is associated with suboptimal MIRQ, the findings have not been consistent. Personality characteristics are associated with parenting and proneness to depression, presenting a potential addition to prenatal mental health assessment. We conducted a systematic review of studies that have examined the link between prenatal depressive symptoms and/or personality characteristics with postnatal MIRQ. Our findings suggest that both maternal personality traits and depressive symptoms measured in early pregnancy are associated with postnatal MIRQ. A measure of personality characteristics may enhance prenatal mental health assessment, affording opportunities for targeted intervention commencing in pregnancy to improve MIRQ, parenting, maternal mental health outcomes, and infant psychosocial and psychological development, and thereby contributing to the reduction of human and economic cost burdens.