The interactions between avian brood parasites and their hosts have become widely recognised as model systems for studying coevolutionary processes. These systems have traditionally been viewed as relationships between one species of brood parasite and one species of host; however, with most brood parasites being known to parasitise multiple species of host and hosts often being subject to parasitism by multiple brood parasite species, opportunities to examine the ecology and evolution of multispecies interactions have generally been overlooked. Here, we compile data on all known brood parasite–host relationships and investigate where and how multiple species of brood parasites and hosts coexist. Considering these relationships as interactions in ecological networks, we find that complex brood parasite–host systems (i.e. those that include multiple species of brood parasites and hosts) exhibiting highly connected networks are found globally, with increased prevalence at lower latitudes in tropical and sub-tropical ecosystems. We also examine patterns of past research, outline the disparity between global patterns of network complexity and past research emphases, and discuss spatial and temporal factors that may be associated with these observed patterns. Drawing on insights gained from the handful of brood parasitism studies involving more complex scenarios and other biological systems that have embraced the use of a multispecies framework, we highlight the potential benefits of considering brood parasite–host interactions as ecological networks and brood parasitism as a model system for studying multispecies interactions. Overall, our results provide new insights into the diversity of these relationships when considered in a multispecies framework, highlight the stark mismatch between past research efforts and global patterns of system complexity, and draw attention to the opportunities that the study of more complex arrangements offers for examining how species interactions shape global patterns of biodiversity.