Purpose: This study aims to investigate the effects of external factors on logistics firms' green logistics (GLs). Based on the literature review, the factors affecting GLs are determined, including the Government's regulatory pressure, the GLs system's perfection, the GLs industry's development level, and customer pressure. This study also identifies five components reflecting GLs practices: green packaging practices, fuel efficiency practices, optimization of routes practices, carbon emissions measurement practices, and reserve GLs. This research proposes hypotheses that indicate the direct impact of external factors on GLs practices of logistic firms. Research design, data, and methodology: By surveying 281 middle and senior managers who are representative of 281 logistics firms operating in Vietnam, the PLS-SEM was used to analyze data. Results: The research findings reveal the significant effect of three external factors, including the perfection of the GLs system, the development level of the GLs industry, and customer pressure to encourage logistics firms to apply GL practices in their business. Conclusion: By investigating the multi-dimensional constructs of GLs, this study has provided a comprehensive picture of GLs in Vietnam and clarified the importance of external factors from government, industry context, and customer requirements in promoting GLs activities in logistics firms in Vietnam.