CD4 T cells and the cytokines IL-4 and IL-13 are required for primary immunity to helminthes and for allergic responses. Although T-helper-2 (Th2) cells are believed to provide protection, genetic deletion of IL-4/13 from CD4 T cells revealed that cytokines from innate cells mediate Nippostrongylus brasiliensis clearance and survival after Schistosoma mansoni infection. Basophils were the only IL-4-secreting innate cells identified. Basophils were recruited to numerous sites, but basophil cytokine secretion occurred only in affected tissues, and was independent of CD4 T cell-derived IL-4/13 and IgE. Depletion of basophils compromised the ability to expel intestinal helminthes. Thus, basophils serve as innate effector cells during primary helminth infection by secreting cytokines at sites of tissue involvement, a process amplified during adaptive immunity by IgE through IL-4-mediated T cell help.