Cancer is a systemic disease with complications beyond the primary tumor site. Among them, thrombosis is the second leading cause of death in patients with certain cancers (e.g., pancreatic ductal adenocarcinoma [PDAC]) and advanced-stage disease. Here, we demonstrate that pro-thrombotic small extracellular vesicles (sEVs) are secreted by C-X-C motif chemokine 13 (CXCL13)-reprogrammed interstitial macrophages in the non-metastatic lung microenvironment of multiple cancers, a niche that we define as the pro-thrombotic niche (PTN). These sEVs package clustered integrin beta(2) that dimerizes with integrin alpha(X) and interacts with platelet-bound glycoprotein (GP)Ib to induce platelet aggregation. Blocking integrin beta(2) decreases both sEV-induced thrombosis and lung metastasis. Importantly, sEV-beta(2) levels are elevated in the plasma of PDAC patients prior to thrombotic events compared with patients with no history of thrombosis. We show that lung PTN establishment is a systemic consequence of cancer progression and identify sEV-beta(2) as a prognostic biomarker of thrombosis risk as well as a target to prevent thrombosis and metastasis.