The circular economy has emerged as an important approach in addressing how society can use its resources more efficiently. Theoretical advancements in the circular economy have yielded benefits for both practice and policymaking. However, if the eco-efficiency of resource use is to be improved, then certain challenges that face the circular economy must be resolved. One of these challenges concerns the rebound effect. By investigating resource flow with a circular (rather than linear) system, as well as within a producer-producer (rather than producer-consumer) type of relationship, we identify a rebound effect that we term 'symbiotic rebound'. We differentiate it from other forms of rebound effect on the basis of its main driver: Opportunity costs drive a higher than expected use of resources in a circular economy, rather than the usual driver of 'demand', as found in other types of rebound. In identifying, describing, and illustrating a symbiotic rebound effect, we make two contributions: first to the rebound literature, and second to theory development on the circular economy.