We propose a systemic-constructivist perspective for analyzing knowledge construction. In contrast to theories that focus on individuals as actors, the systemic-constructivist approach emphasizes the relevance of social systems and regards the construction of knowledge as a self-referential process that takes place in social systems. We propose that it is the system that defines what is accepted as legitimate knowledge and thus shapes individuals' behavior. We present this approach and its implications by providing a case study of knowledge construction in Wikipedia. We analyzed the article about the Fukushima Daiichi nuclear power plant shortly after the nuclear catastrophe unfolded. There was a flood of highly uncertain information circulating, which the social system Wikipedia had to deal with and make meaning of. We obtained a group of very diverse people who largely lacked specific background education on the topic but accomplished the collaborative creation of an article that was later considered by experts to be of high quality. By interpreting these occurrences as operations of a social system, we aim to extend the theoretical basis of the learning sciences with an approach that emphasizes systems and their structures instead of individuals or groups. We discuss how this perspective may contribute to understanding collaborative knowledge construction.