A Trial of labor after cesarean section is an attempt to deliver vaginally by a woman who had a previous cesarean delivery and when achieved by a vaginal delivery it is called successful vaginal birth after cesarean section. Vaginal birth after a caesarian section is a preferred method to decrease complications associated with repeated caesarian section delivery for both mother and fetus. It has a higher success rate when the right women are selected for a trial of labor. This study aimed to assess factors associated with successful vaginal birth after one lower uterine transverse cesarean section and to validate the Flamm and Geiger score at the public hospitals of Bahir Dar City, Northwest, Ethiopia, 2021. A health facility-based retrospective cross-sectional study was conducted from March 1 to 15/2021. A medical record review of 408 women charts with a trial of labor after one lower uterine transverse cesarean section from January 1/2020 to December 31/2020 was done and 345 women charts with complete maternal and fetal information were included in the study with a response rate of 84.6%. The data were collected using a structured checklist, entered into Epi data 3.1, and analyzed using SPSS 25.0 version. Logistic regression analyses were done to estimate the crude and adjusted odds ratio with a confidence interval of 95% and a P-value of less than 0.05 considered statistically significant. This study identified that the trial of labor after cesarean section rate was 69.5%, and the success rate of vaginal birth after one lower uterine transverse cesarean section was 35.07%. Of the failed trial of labor, fetal distress (38.9%) and failed progress of labor (32.1%) were the main indications for an emergency cesarean section. The maternal age group of 21–30 years, prior vaginal birth after or before cesarean section, non-recurring indication (fetal distress and malpresentation), ruptured membrane, cervical dilatation ≥ 4 cm, cervical effacement ≥ 50%, and low station (≥ 0) at admission were associated with successful vaginal birth after one lower uterine transverse cesarean section. For the Flamm and Geiger score at a cut point of 5, the sensitivity and specificity were 73.6% and 86.6% respectively. In this study area, the trial of labor after cesarean section rate is encouraging, however, the success rate of vaginal birth after one lower uterine transverse caesarian section was lower. The maternal socio-demographic and obstetric-related factors were significantly associated with successful vaginal birth after one lower transverse caesarian section delivery. This study indicated that when the Flamm and Geiger score increases, the chance of successful vaginal birth after one lower uterine transverse caesarian section also increases. We suggest emphasizing counselling and encouraging the women, as their chance of successful vaginal delivery will be high in the subsequent pregnancy, especially if the indications of primary caesarian section delivery were non-recurring.