Postpartum women experience various changes in their physical and psychological health and in their relationships with their spouse and newborn. This study aimed to identify and evaluate the factors that affect the quality of life (QoL) of women within six weeks after childbirth. A prospective, cross-sectional correlational study was used. A convenience sample of 179 postpartum women was recruited from four postpartum care centers in South Korea. Participants completed structured questionnaires on postpartum fatigue, postpartum depression, marital intimacy, breastfeeding adaptation, and quality of life. Marital intimacy (β = 0.466, p < 0.001) was the most influencing factor on the QoL of women during the postpartum period. In descending order, postpartum fatigue (β = −0.192, p = 0.001), postpartum depression (β = −0.190, p = 0.001), breastfeeding adaptation (β = 0.163, p = 0.002), and occupation (β = 0.163, p = 0.004) all had a significant influence on QoL (F = 32.09, p < 0.001), and the overall explanatory power was 63.6%. It is necessary to assess and consider the physical, psychological, relational, and demographic factors of women during the early postpartum period. Comprehensive interventions need to be developed to improve the QoL of women during the postpartum period.