OBJECTIVE Under-reporting is a major drawback of a voluntary adverse drug reaction reporting system in pharmacovigilance. However, little is known about facilitators and barriers to ADR reporting by healthcare professionals (HCPs) in developing countries. To investigate factors associated with adverse drug reaction (ADR) reporting among HCPs in Vietnam. METHODS A cross-sectional survey of 2091 HCPs was conducted in 2015 at 10 hospitals throughout Vietnam. The binary outcome was ever reporting ADRs. Healthcare professionals knowledge, attitude and practice about ADR reporting were measured. Multiple logistic regression analyses examined factors significantly associated with ever ADR reporting. RESULTS Overall, 29.3%, 2.2% and 68.4% of the sample were doctors, pharmacists and nurses, respectively. More than half (59.3%) had ever reported any ADR. Facilitators for ADR reporting were educational training (OR = 1.77, 95%CI = 1.42-2.22) and having better knowledge, such as awareness of ADR reporting regulation (OR = 1.63, 95%CI = 1.19-2.21), of reporting time (OR = 1.76, 95%CI = 1.35-2.29) and of necessary information in reporting form (OR = 1.94, 95%CI = 1.53-2.45).Conversely, barriers to non-reporting were unknown of reporting procedure (OR = 0.27, 95%CI = 0.22-0.35), unavailability of reporting form (OR = 0.54, 95%CI = 0.42-0.68) and lack of time (OR = 0.59, 95%CI = 0.46-0.74). CONCLUSIONS Given the low ADR reporting rate among HCPs, educational interventions to improve their knowledge and attitude should be prioritized in Vietnam. Additional interventions addressing obstacles (i.e. availability and complexity of reporting form, lack of time) should be considered to improve both the quantity and quality of ADR reporting.