||Artificial light at night is an increasing threat for ecological processes. Previous work has highlighted the effects of nighttime light on individuals and on higher levels of biological organization, such as community ecology and ecosystem functioning. Here, we focus on the effects of artificial light at night on social interactions and group dynamics. We discuss 4 main ways of how light pollution is expected to alter social interactions and group dynamics. First, light at night can alter the activity patterns of individuals and this is predicted to affect the social network structure of populations, which in turn affects the transfer of information and diseases. Second, changes in activity patterns and disrupted biological rhythms are expected to reduce behavioral synchrony in social processes such as reproduction, migration, and dispersal. Third, increased light at night is expected to affect the communication between individuals; primarily, it will increase the opportunities for visual social information transfer. Last, artificial nighttime light is expected to lower social competence, with subsequent negative effects on aggressive interactions and group coordination. Throughout the article, we propose testable hypotheses and identify suitable study species, and we hope that this article inspires future research on the effects of bright nights on social interactions and group dynamics.