BackgroundBreech presentation is observed in 3–4% at term of pregnancy and is one of the leading causes of cesarean section. There is no established treatment for breech presentation before 36 weeks. A retrospective cohort study was conducted to demonstrate that the lateral position is effective for breech presentation. However, there are no randomized controlled trials evaluating lateral position management for breech presentation. Here, we described the methodology of a randomized controlled trial of a cephalic version for breech presentation in the third trimester by lateral postural management (BRLT study).MethodsThe BRLT study is an open-label, randomized controlled trial with two parallel groups allocated in a 1:1 ratio to examine the lateral position management for breech presentation, as compared with expectant management care. An academic hospital in Japan will enroll 200 patients diagnosed with a breech presentation by ultrasonography between 28 + 0 weeks and 30 + 0 weeks. Participants in the intervention group will be instructed to lie on their right sides for 15 min three times per day if the fetal back was on the left side or lie on their left sides if the fetal back was on the right side. The instruction will be given every 2 weeks after confirmation of fetal position, and the lateral position will be instructed until the cephalic version, and after the cephalic version, the reverse lateral position will be instructed until delivery. The primary outcome is cephalic presentation at term. The secondary outcomes are cesarean delivery, cephalic presentation 2, 4, and 6 weeks after the instruction, and at delivery, recurrent breech presentation after cephalic version, and adverse effects.DiscussionThis trial will answer whether the lateral positioning technique is effective in treating breech presentation and, depending on the results, may provide a very simple, less painful, and safe option for treating breech presentation before 36 weeks, and it may impact breech presentation treatment.Trial registrationUMIN Clinical Trials Registry UMIN000043613. Registered on 15 March 2021https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000049800.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13063-023-07395-w.