Tumor endothelial cells (ECs) promote cancer progression in ways beyond their role as conduits supporting metabolism. However, it is not understood how vascular niche-derived paracrine factors, known as angiocrine factors, provoke tumor aggressiveness. Here, we show that FGF4 produced by B-Cell lymphoma cells (LCs) through activating FGFR1 upregulates the Notch-ligand Jagged1 (Jag1) on neighboring tumor ECs. In turn, upregulation of Jag1 on ECs reciprocally induces Notch2-Hey1 in LCs. This crosstalk enforces aggressive CD44+IGF1R+CSF1R+ LC phenotypes, including extra-nodal invasion and chemoresistance. Inducible EC-selective deletion of Fgfr1 or Jag1 in the Eμ-Myc lymphoma model or impairing Notch2 signaling in mouse and human LCs diminished lymphoma aggressiveness and prolonged mouse survival. Thus, targeting the angiocrine FGF4-FGFR1/Jag1-Notch2 loop could inhibit LC aggressiveness and enhance chemosensitivity.