Despite continuous exposure to trillions of microbes, the intestinal immune system protects the mucosa by balancing barrier protection, tolerance, and immunity. As both sentinel and effector, the mucosal innate immune system plays a central role in coordinating these responses. By integrating signals from the intestinal microbiota, mononuclear phagocytes (MNPs) serve as a critical link in regulating effector functions of group 3 innate lymphoid cells (ILC3s). Our recent work identified the role for MNP production of the IBD-linked protein TNF-like ligand 1A (TL1A) in modulating microbial regulation of ILC3 barrier immunity. These findings highlight a broader role for ILC3s in local control of T cell immunity and their potential role in the pathogenesis and treatment of inflammatory disease.