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.