Thymic stromal lymphopoietin (TSLP) is an interleukin 7 (IL-7)-like cytokine originally characterized by its ability to promote the activation of B cells and dendritic cells (DCs). Subsequent studies have shown that TSLP promotes T helper type 2 (T_H2) cell responses associated with immunity to some helminth parasites and the pathogenesis of many inflammatory diseases, including atopic dermatitis and asthma. This review will focus on recent findings indicating that in addition to influencing B cell and DC function, TSLP can promote T_H2 cytokine–associated inflammation by directly promoting the effector functions of CD4⁺ T_H2 cells, basophils and other granulocyte populations while simultaneously limiting the expression of DC-derived proinflammatory cytokines and promoting regulatory T cell responses in peripheral tissues.