This study critically examines the European Union’s evolving legal approach to combating greenwashing, with a particular focus on the Proposal for a Green Claims Directive (GCD) and related legislative initiatives under the European Green Deal. Employing systematization, analytical–synthetic methods, and comparative legal analysis, the research identifies substantive shortcomings in Vietnam’s current framework, including the absence of explicit rules on environmental claims and the lack of independent verification mechanisms. The findings reveal that the GCD Proposal, although not yet adopted, provides a structured and transparent regulatory model through its three core requirements: reliable scientific substantiation, life-cycle assessment, and third-party verification. Drawing on these insights, the paper proposes targeted reforms to Vietnam’s legal system, including the introduction of a statutory definition of greenwashing, the establishment of verification protocols aligned with international standards, and the imposition of sanctions proportionate to the harm caused by deceptive claims. These recommendations aim to enhance consumer protection, foster genuine sustainable business practices, and align Vietnam’s regulatory framework with global sustainability goals. By bridging comparative legal insights with domestic policy needs, the article contributes both to academic discourse on environmental law and to the practical advancement of Vietnam’s green transition.