Abstract Background The cesarean section rate in Vietnam has been increasing especially in urban area. However, limited evidence identified regarding socio-demographic factors of the cesarean section birth. The objective of this study was to determine the current cesarean birth rate and the associated socio-demographic factors among mothers in Nha Trang city, south-central Vietnam. Methods A community-based cross-sectional study was conducted between October and November in 2016 as part of a Streptococcus pneumoniae carriage survey conducted in 27 communes of Nha Trang city. From each commune, 120 mothers and their children less than 2 years old were randomly selected. Mothers were asked to answer standardized questions regarding socio-demographic information and mode of birth. Multivariate logistic regression was adopted to examine associations between socio-demographic variables and mode of birth. Results Of 3148 participants, the number of cesarean births was 1396 (44.3 %). Older maternal age (≥ 30 years old), having another child going to school or kindergarten, monthly income more than 644 USD, gestational weeks at birth over 42 weeks, and low (< 2500 g) or high (≥ 3500 g) birth weight were associated with higher likelihood of cesarean births. Conclusion The CS rate obtained in this study was more than twice of what is recommended by the World Health Organization, which is consistent with the previous nation-wide study in Viet Nam. Further monitoring is suggested to examine the non-medical reason for the increased CS rate.