National Action Plans (NAPs) are a possible implementation measure for the Global Plastics Treaty, through a NAP-based approach. Their effectiveness in other international agreements is contested, and their current format allows for weak, voluntary measures with limited accountability. By analysing stakeholder and country submissions to the Intergovernmental Negotiating Committee (INC) secretariat ahead of INC-2 negotiations in Paris, June 2023, conducting a literature review, and interviewing key actors, this study aims to determine the support that governments and stakeholders have for a NAP-based approach in the Treaty, and identify the key enablers needed to ensure that NAP-based approaches, if adopted in the Treaty, are effective. Results indicate that by INC-2, more than 85% of countries supported a NAP-based approach, suggesting a high chance of this approach being selected as the means of implementation of the Treaty. However, interviewees and literature reviews indicate that NAPs in their current form are not likely to be effective at delivering ambitious Treaty targets. Six key enablers to improve the effectiveness of plastics NAPs are identified. These enablers should be integrated into any plastics NAPs both independently, and as potential requirements of the Treaty to ensure that NAP-based approaches are effective and have the impact intended.