From a mouse model of hypoxia-induced pulmonary hypertension, we previously found a highly upregulated protein in the lung that we named hypoxia-induced mitogenic factor (HIMF), also known as found in inflammatory zone (FIZZ) 1, and resistin-like molecule alpha (RELM). However, the mechanisms of HIMF in the pulmonary vascular remodeling remain unknown. We now demonstrate that HIMF promoted cell proliferation, migration, and the production of vascular endothelial growth factor (VEGF) and monocyte chemotactic protein-1 (MCP-1) in pulmonary endothelial cells, as well as the production of reactive oxygen species (ROS) in murine monocyte/macrophage cells. HIMF-induced CD31-positive cell infiltrate in in vivo Matrigel plugs was significantly suppressed by VEGF receptor-2 (VEGFR2) blockade. In ex vivo studies, HIMF stimulated the production of VEGF, MCP-1 and stromal derived factor -1 (SDF-1) in the lung resident cells, and VEGFR2 neutralization significantly suppressed HIMF-induced MCP-1 and SDF-1 production. Furthermore, intravenous injection of HIMF showed marked increase of CD68-positive inflammatory cells in the lungs, and these events were attenuated by VEGFR2 neutralization. Intravenous injection of HIMF also down-regulated the expression of VEGFR2 in the lung. These results suggest that HIMF plays critical roles in pulmonary inflammation as well as angiogenesis.