Dysregulated inflammation contributes to disease pathogenesis in both the periphery and the brain. Cytokines are coordinators of inflammation and were originally defined as secreted mediators, released from expressing cells to activate plasma membrane receptors on responsive cells. However, a group of cytokines is now recognized as having dual functionality. In addition to their extracellular effects, these cytokines act inside the nuclei of cytokine-expressing or cytokine-responsive cells. Interleukin-1 (IL-1) family cytokines are key pro-inflammatory mediators, and blockade of the IL-1 system in inflammatory diseases is an attractive therapeutic goal. All current therapies target IL-1 extracellular actions. Here we review evidence that suggests IL-1 family members have dual functionality. Several IL-1 family members have been detected inside the nuclei of IL-1-expressing or IL-1-responsive cells, and intranuclear IL-1 is reported to regulate gene transcription and mRNA splicing. However, further work is required to determine the impact of IL-1 intranuclear actions on disease pathogenesis. The intranuclear actions of IL-1 family members represent a new and potentially important area of IL-1 biology and may have implications for the future development of anti-IL-1 therapies.