The objective of this review was to determine the timing of overall and cause-specific maternal mortality and severe morbidity during the postpartum period. Many women continue to die or experience adverse health outcomes in the postpartum period; however, limited work has explored the timing of when women die or present complications during this period globally. This review considered studies that reported on women after birth up to 6 weeks postpartum and included data on mortality and/or morbidity on the first day, days 2-7, and days 8-42. Studies that reported solely on high-risk women (eg, those with antenatal or intrapartum complications) were excluded, but mixed population samples were included (eg, low-risk and high-risk women). MEDLINE, Embase, Web of Science, and CINAHL were searched for published studies on December 20, 2019, and searches were updated on May 11, 2021. Critical appraisal was undertaken by 2 independent reviewers using standardized critical appraisal instruments from JBI. Quantitative data were extracted from included studies independently by at least 2 reviewers using a study-specific data extraction form. Quantitative data were pooled, where possible. Identified studies were used to obtain the summary estimate (proportion) for each time point. Maternal mortality was calculated as the maternal deaths during a given period over the total number of maternal deaths known during the postpartum period. For cause-specific analysis, number of deaths due to a specific cause was the numerator, while the total number of women who died due to the same cause in that period was the denominator. Random effects models were run to pool incidence proportion for relative risk of overall maternal deaths. Subgroup analysis was conducted according to country income classification and by date (ie, data collection before or after 2010). Where statistical pooling was not possible, the findings were reported narratively. A total of 32 studies reported on maternal outcomes from 17 reports, all reporting on mixed populations. Most maternal deaths occurred on the first day (48.9%), with 24.5% of deaths occurring between days 2 and 7, and 24.9% occurring between days 8 and 42. Maternal mortality due to postpartum hemorrhage and embolism occurred predominantly on the first day (79.1% and 58.2%, respectively). Most deaths due to postpartum eclampsia and hypertensive disorders occurred within the first week (44.3% on day 1 and 37.1% on days 2-7). Most deaths due to infection occurred between days 8 and 42 (61.3%). Due to heterogeneity, maternal morbidity data are described narratively, with morbidity predominantly occurring within the first 2 weeks. The mean critical appraisal score across all included studies was 85.9% (standard deviation = 13.6%). Women experience mortality throughout the entire postpartum period, with the highest mortality rate on the first day. Access to high-quality care during the postpartum period, including enhanced frequency and quality of postpartum assessments during the first 42 days after birth, is essential to improving maternal outcomes and to continue reducing maternal mortality and morbidity worldwide. PROSPERO CRD42020187341.