Introduction The success of the WHO Framework Convention on Tobacco Control (FCTC) depends on parties’ active participation in its governance and implementation, particularly via biennial Conference of the Parties (COP) meetings. The COP’s efficacy is threatened by declining attendance and reductions in travel support for low-income and middle-income countries, and there are growing concerns about transparency and representation in country delegations amid industry efforts to shape their composition.

Methods We examined parties’ participation in the COP based on official meeting records, and the relationship between attendance and strength of tobacco control based on national global tobacco control reports.

Results Attendance at the COP has decreased over time, and at several meetings would have fallen below 66% (the threshold for decision-making) if it was not for high levels of participation among low-income and lower-middle-income countries. Despite their higher attendance at COP meetings, these countries represent a smaller share of meeting attendees due to the smaller size of their delegations. Additionally, there has been a decline in the proportion of delegates from ministries of health and tobacco control focal points. Nationally, COP participation is correlated with stronger tobacco control policies; attendance by low-income countries has a strong correlation with implementation of advertising bans, while attendance among high-income and lower-middle-income countries shows a moderate correlation with implementation of tobacco taxes.

Conclusions Supporting states to actively engage in the COP is crucial for ongoing FCTC implementation, strengthening national capacity for tobacco control, and protecting the legitimacy and efficacy of global health governance.