Based on studies by our group and others, we hypothesized that IL-7 may possess antifibrotic activities in an IFN-γ–dependent and independent manner. Here, we have evaluated the antifibrotic therapeutic potential of IL-7 in both in vitro and in vivo pulmonary fibrosis models. IL-7 inhibited both TGF-β production and signaling in fibroblasts and required an intact JAK1/STAT1 signal transduction pathway. IL-7–mediated inhibition of TGF-β signaling was found to be associated with an increase in Smad7, a major inhibitory regulator in the SMAD family. In the presence of IL-7, Smad7 dominant negative fibroblasts restored TGF-β–induced collagen synthesis, indicating that an IL-7–mediated increase in Smad7 suppressed TGF-β signaling. Consistent with these in vitro findings, recombinant IL-7 decreased bleomycin-induced pulmonary fibrosis in vivo, independent of IFN-γ. The antifibrotic activities of IL-7 merit further basic and clinical investigation for the treatment of pulmonary fibrosis.