Background: In several African nations, including Ethiopia, improving mother and child health is a top public health concern. Unfortunately, there is a dearth of study on pregnant women in Ethiopia who concomitantly utilize pharmaceutical drugs and medicinal plants. Hence, the objective of this research was to assess the concomitant use of pharmaceutical drugs and medicinal plants among pregnant women in Southern Ethiopia in 2021. Methods: A community-based cross-sectional study was conducted among systematically selected 400 pregnant women in Shashamane town, Southern Ethiopia, from July 1–30/2021. An interviewer-administered structured questionnaire was used to collect data. Binary logistic regression was performed to examine the association between a dependent variable and independent variables. Results: According to this study, among those who self-medicated, 90 (22.5%) reported using at least one pharmaceutical drug, while 180 (45%) reported using at least one medicinal plant. Moreover, 68 (17%) of the participants who had taken drugs while pregnant also used pharmaceutical drugs and medicinal plants concomitantly. Having a medical condition during pregnancy (AOR = 5.6, 95% CI: 2.7–11.6), not having ANC follow up (AOR = 2.9, 95% CI: 1.3–6.2), gestational age (AOR = 4.2, 95% CI: 1.6–10.7), and not having a formal education (AOR = 4.2, 95% CI: 1.3–13.4) were all significantly associated with concomitant use of pharmaceutical drugs and medicinal plants during pregnancy. Conclusion: This study showed that nearly one in five pregnant women used medicinal plants concomitantly with pharmaceutical drugs. Mother's educational status, medical illness during pregnancy, having ANC follow up and gestational period were significantly associated with concomitant use of medicinal plants and pharmaceutical drugs. Therefore, health care providers and concerned stakeholders should consider these factors to minimize the risks associated with drug use during pregnancy on both mother and fetus.