Much negotiation research assumes that countries participate in multilateral negotiations to influence negotiation outcomes, and has sought to evaluate that influence over outcomes in different ways. Much less attention has been paid to participation itself, that is, how active countries are in negotiations. Yet, countries vary strongly in the extent to which they engage in multilateral processes, with some countries being highly vocal and visible, and others, rather passive and invisible. What explains this variation? Our dataset compiles data on participation in negotiations from COP1 in 1995 to COP28 in 2023. Using sources such as the Earth Negotiation Bulletin and UNFCCC records, we develop a participation index that tracks oral interventions, written submissions, leadership roles, and press briefings to measure engagement. We analyze this data with a time-series cross section model to explain how and why countries engage in negotiations. Theoretically, if states are rational and aim to influence outcomes, they would all seek active participation, but varying capacities may limit this. We hypothesize that resource constraints impact delegation size, affecting participation, with larger delegations typically playing more active roles. For smaller delegations, personal commitment of experienced negotiators can increase a country’s visibility. Thus, our second hypothesis links participation to delegation experience and continuity. By focusing on participation rather than negotiation size, our research sheds light on the dynamics that shape multilateral climate negotiations and their outcomes, and provides insights into the mechanisms that drive negotiation effectiveness and equity.