Background: The postpartum period is the most crucial but also the most fragile stage of most pregnancies. The health benefits of aromatherapy have recently become more widely accepted among medical experts. Although a number of studies have examined these health benefits, no systematic reviews have been conducted to assess the effects of aromatherapy on the psycho-physiological health of postpartum women. Purpose: This systematic review was conducted to evaluate the effectiveness of aromatherapy interventions on the psycho-physiological health of postpartum women, to determine the methods that were used to measure intervention effectiveness, and to identify the types of interventions that were used. Methods: We searched for studies that evaluated the effects of aromatherapy on postpartum women published in the Chinese or English languages before March 2018. We used online databases such as the Taiwan Journal Index, Centre for European Policy Studies, Cumulative Index for Nursing and Allied Health Literature, Cochrane Library, PubMed, and Social Sciences Citation Index. The search keywords used were "women," AND "postpartum," OR "postnatal" AND "aromatherapy," OR "aroma," OR "essential oils." Only randomized controlled trials including humans as study participants were included. The methodological quality of the trials was assessed using the modified Jadad scale. The quality of the full-text studies was assessed by three reviewers. Results: The 15 studies that were included in this systematic review were performed in Iran, England, and the United States and included 2,131 participants in total. The numbers of participants in each study ranged between 35 and 635. The review found that the effective duration of aromatherapy varied according to the essential oils that were selected. The visual analog scale was the most frequently used measure of postpartum pain. Most of the studies found that the aromatherapy intervention improved postpartum physiological and psychological health, with positive effects shown on anxiety, depression, distress, fatigue, mood, nipple fissure pain, physical pain, post-cesarean-delivery pain, post-cesarean-delivery nausea, postepisiotomy pain, postepisiotomy recovery, sleep quality, and stress. Most of the studies reported no serious intervention-related side effects. Conclusions: This systematic review may serve as a reference for healthcare workers in caring for postpartum women. Aromatherapy may be applied as a noninvasive complementary intervention to promote physio-psychological comfort in postpartum women.