Background Shared decision-making between clinicians and pregnant women with prior cesarean on the subsequent mode of delivery improves trial of labor rates, and reduces the number of repeat cesarean sections and their related complications. However, this practice is insufficient worldwide and the factors influencing it are still unknown. The study aimed at determining the proportion of pregnant women involved in shared decision-making and its associated factors in Dar es Salaam. Methods A cross-sectional analytical study among 350 pregnant women with one prior cesarean section. Data was collected using a structured questionnaire and SPSS 23 was used for analysis. A score of 80 or higher on the nine-item Shared Decision-Making Questionnaire (SDM-Q9) was used to calculate the proportion of women, and the associated factors were obtained using a logistic regression model. P value of < 0.05 was considered significant. Results The proportion of pregnant women involved in shared decision making was 38%. Factors that were significantly associated with sharing decision making were; having low level of education (AOR 0.55 95% CI 0.33–0.91), being married/having partner (AOR 2.58 95% CI 1.43–4.63), having a companion who had active participation (AOR 3.31 95% CI 1.03–10.6) and being familiar with the clinician (AOR 5.01 95% CI 1.30–19.2). Conclusion To promote practice of shared decision making in our setting, encouragement of socially vulnerable pregnant women’s participation in decision-making by health care professionals, encouragement of companion participation during antenatal care and promotion of personal continuity of care to improve familiarity to clinicians are needed.