The activity of a variety of extracellular signaling factors is tightly regulated by proteins containing A Disintegrin And a Metalloprotease domain (ADAM) metalloproteases through limited proteolysis. Thus, the identification of ADAM substrates may unveil novel components and mechanisms of cell signaling pathways. We report the identification of the transmembrane protein vasorin (VASN), a transforming growth factor-β (TGFβ) trap, as a substrate of ADAM17. The metalloprotease efficiently generates a soluble fragment encompassing the extracellular domain of VASN. Despite the importance of TGFβ in normal development and tumor progression, the regulation of VASN is completely unknown. Here, we show that only the soluble form of VASN inhibits TGFβ and that the secretion of VASN is tightly controlled by ADAM17. Hence, inhibition of ADAM17 leads to the upregulation of TGFβ signaling. Adding a new level of complexity to the function of ADAM17, we finally show that, through the cleavage of VASN, the metalloprotease controls TGFβ-mediated epithelial-to-mesenchymal transition.