Decorin is a stromal-derived prototype member of the small leucine-rich proteoglycan gene family. In addition to its functions as a regulator of collagen fibrillogenesis and TGFb activity, soluble decorin acts as a pan-receptor tyrosine kinase (RTK) inhibitor. Decorin binds to various RTKs, including EGFR, HER2, HGFR/Met, VEGFR2, TLR and IGFR. Although the molecular mechanism for the action of decorin on these receptors is not entirely elucidated; overall, decorin evokes transient activation of these receptors with suppression of downstream signaling cascades culminating in growth inhibition, followed by their physical downregulation via caveosomal internalization and degradation. In the case of Met, decorin leads to decreased b-catenin signaling pathway and growth suppression. As most of these RTKs are responsible for providing a growth advantage to cancer cells, the result of decorin treatment is oncosuppression. Another decorin-driven mechanism to restrict cancer growth and dissemination is by impeding angiogenesis via VEGFR2 and the concurrent activation of protracted endothelial cell autophagy. In this review, we will dissect the multiple roles of decorin in cancer biology and its potential use as a next-generation protein-based adjuvant therapy to combat cancer.