The COVID-19 pandemic has placed a considerable burden on frontline healthcare workers (HCWs), thus increasing their vulnerability to developing posttraumatic stress disorder (PTSD). Our study aimed to examine the relationship between possible PTSD symptoms and resilience and identify associated factors with possible PTSD symptoms among Vietnamese frontline HCWs during the COVID-19 pandemic in 2021. We conducted a cross-sectional study across medical facilities at three administrative levels: provincial, district, and commune levels of Vietnam's healthcare service and management systems. The Item of Event Scale-Revised (IES-R) and Brief Resilience Scale (BRS) were used to measure possible PTSD symptoms and psychological resilience accordingly. In the sample of 763 HCWs, two-thirds were women, their median age was 34, and nearly half were nurses. 15.9% of HCWs reported having possible PTSD symptoms. Several variables, including COVID-19 concerns: worried about being infected with COVID-19, lacking personal protective equipment (PPE), about an uncontrollable pandemic, feeling lonely about being isolated from family, and resilience capacity were statistically significant with having possible PTSD symptoms. Multiple logistic regression showed that reused PPE, concerns about lacking PPE, and low levels of resilience were significantly associated with an increased likelihood of possible PTSD symptoms. It is suggested that greater priority should be given to improving healthcare plans to mitigate HCWs' PTSD symptoms and improve their resilience trait.