Background: In Tanzania, the use of locally-grown herbs during pregnancy is common. Some herbs used during pregnancy have been associated with pregnancy, delivery, and postpartum complications. The prevalence of use and characteristics of women in Kigoma who use herbs during pregnancy and/or labor, and the associations between local herb use and postpartum complications, have not been well described. Methods: We analyzed births reported between January 2014 and September 2016 to the Kigoma Tanzania Reproductive Health Survey, a regionally representative, population-based survey of reproductive age women (15–49 years) about fertility, contraception, and maternal and newborn health. We conducted weighted descriptive analyses of reported herb use, reasons for use during pregnancy, and associations with postpartum complications. We used multivariable logistic regression to calculate adjusted odds ratios (aOR) and 95% confidence intervals (CI) for factors associated with use of local herbs during pregnancy. Results: Of the 3,530 reported births, 10.9% (CI: 9.0–13.1) of women indicated use of local herbs during their last pregnancy and/or labor. Common reasons for taking local herbs included stomach pain (42.9%), fetal health (25.5%), and miscarriage avoidance (21.6%). The model found the adjusted odds of local herb use during pregnancy and/or labor were higher for women reporting home versus facility-based delivery (aOR: 1.6, CI: 1.1–2.2), having one versus multiple children (aOR: 1.8, CI: 1.4–2.4), and belonging to the lowest as compared to the highest household wealth tercile (aOR: 1.4, CI: 1.1–1.9). Odds of having a postpartum complication was significantly higher among women who used herbs during pregnancy and/or labor (OR: 1.5 CI: 1.1–1.8). We found no association between postpartum complications and residence, birth order, delivery location, wealth tertile, age group, and educational level. Conclusions: In Kigoma, approximately one in ten women used local herbs during their last pregnancy and/or labor; use was associated with wealth, parity, and home delivery. Postpartum complications were associated with local herb use by pregnant women in this region. Better understanding which herbs are used and how local herb use effects pregnancy, delivery, or postpartum complications could help to prevent adverse exposures and outcomes among pregnant women in Kigoma.