Collective marketing is a proven strategy to improve market access for small-scale producers and reduce poverty through increased income. In this study, four groups of smallholders in Honduras and Nicaragua were studied to explore whether indicators of social capital can be used to predict success in setting up collective marketing. A baseline assessment of the groups’ social capital endowments during the pre-marketing phase is compared with their marketing success after two years. Results show that the groups’ different initial levels of social capital were not directly linked with market success. All groups built up relevant social capital during the establishment phase with external support, although some members left the groups. For determining how to provide support to emerging group marketing, the commonly used measures for social capital to predict success are therefore not sufficient. Additional indicators are needed - such as access to assets and start-up skills of members - for assessing the capacity of groups for continuous construction of social capital in a dynamic process.