Objectives: Vietnam has witnessed a severe shortage of qualified staff in the public health sector after the COVID-19 pandemic. Our cross-sectional study aimed to identify job motivation and associated factors among experienced frontline health staff working in public health in order to have preventive measures in the event of future pandemics. Methods: A cross-sectional study, from March 2022 to November 2022 at a Vietnamese public hospital, on the job motivation and the predicted factors of 381 healthcare workers who participated in the frontlines of the COVID-19 pandemic from 2020 to 2021. The survey tool, developed by Mbindyo Patrick (2009), includes three components: (i) job satisfaction, (ii) organizational commitment, and (iii) conscientiousness. The survey tool was revalidated in our study with structural equation model for the construction of job motivation model and confirmatory factor analysis for certifying the elementary three components (factors) of the tool. And the tool’s reliability was evaluated by Cronbach’s Alpha. Bivariate analysis and multiple logistic regression were used to identify the predicted factors with the job motivation cutoff of 4.0. Results: The tool for job motivation constructs showed all specifications were good fit indices and the Cronbach’s Alpha was 0.85. The job motivation of health staff decreased dramatically in all dimensions post COVID-19 pandemic, with a mean score of 3.26. Job satisfaction and organizational commitment were the most negatively impacted areas, with scores of 3.02 and 3.00, respectively. The predicted factors of low job motivation were young age (less than 30 years old), low monthly income (less than $400), high qualification, and non-managerial positions with odds ratio of 2.27, 2.5, 2.09, and 3.61, respectively. Conclusion: Following the COVID-19 outbreak in Vietnam, healthcare workers who had been in the frontlines of the COVID-19 pandemic, had experienced a significant decline in their job motivation, despite their continued employment at public hospitals.