Objective To estimate the association of the weight difference between the index trial of labor after cesarean (TOLAC) sonographic estimated fetal weight (sEFW) and prior delivery birth weight with TOLAC success rate among women with previous labor dystocia and no prior vaginal delivery. Methods A retrospective cohort study including all women with prior cesarean for labor dystocia and no prior vaginal delivery undergoing TOLAC during between March 2011 and June 2020 with a sEFW within 1 week from delivery. Results Overall, 168 women were included, of those 107 (63.7%) successfully delivered vaginally. The mean sEFW and mean birth weight were lower in the TOLAC success group (P = 0.010 and P = 0.013, respectively). The rate of higher sEFW in the current delivery compared with the previous delivery did not differ between study groups. The rate of higher TOLAC birth weight was lower in the TOLAC success group (odds ratio 0.30; 95% confidence interval 0.15–0.58). In multivariable regression analysis, maternal age older than 30 years, induction of labor, and higher birth weight were independently negatively associated with TOLAC success (adjusted odds ratio 95% confidence interval: 0.27 0.10–0.70, 0.27 0.08–0.90, and 0.43 0.19–0.94; P = 0.008, P = 0.034, and P = 0.035, respectively). Conclusions sEFW characteristics did not predict the success or failure of TOLAC among women with prior labor dystocia and no previous vaginal delivery. Older maternal age, induction of labor, and higher birth weight are negatively associated with TOLAC success rate among women with prior labor dystocia.