We examined whether women experiencing severe maternal morbidity (SMM) are more likely to be treated for a psychiatric illness or be prescribed psychotropic medications in the postpartum year than mothers who did not experience SMM. We also examine the relationship between SMM and specific mental health-related outcomes, and the relationship between specific SMM diagnoses/procedures and postpartum mental-health-related outcomes. The national registers in Sweden were used to create a population-based matched cohort. Every delivery with SMM between July 1, 2006, and December 31, 2012 (n?=?8558), was matched with two deliveries without SMM (n?=?17,116). Conditional logistic regression models assessed the relationship between SMM and postpartum mental health-related outcomes. Women who experienced SMM had significantly greater odds of being treated for a psychiatric disorder (aOR 1.22; 95% CI 1.03-1.45) and being prescribed psychotropic medications (aOR 1.40; 95% CI 1.24-1.58) in the postpartum year. Specifically, they had significantly greater odds of being treated for neuroses (aOR 1.35; 95% CI 1.09-1.69) and having a prescription for anxiolytics/hypnotics (aOR 1.36; 95% CI 1.18-1.58) or antidepressants (aOR 1.35; 95% CI 1.17-1.55). Women who were diagnosed with shock or uterine rupture/obstetric laparotomy during delivery had the greatest odds of postpartum mental health-related outcomes. This study identified mothers with SMM as a group at high risk for postpartum mental illness. Postpartum mental health services should be provided to ensure the well-being of these high-risk mothers.