Proteinase 3 (PR3) is a serine protease expressed in neutrophils, monocytes, and macrophages. PR3 is a multifunctional protein with a number of proinflammatory properties. For example, PR3 can induce and process pro-inflammatory cytokines including TNFα and IL-1b to enhance their bioactivity and it can also cleave and inactivate anti-inflammatory molecules such as progranulin. Furthermore, it is involved in apoptosis via its interaction with procaspase-3 and when expressed on the surface of dying cells, PR3 promotes inflammation by controlling macrophage activation and delaying the resolution of inflammation. However, most of these observations were made in vitro with very few studies carried out in vivo. Therefore, to better understand the function of PR3 in vivo, we generated a human PR3 transgenic mouse (hPR3Tg). During zymosan-induced peritonitis, hPR3 transgenic mice displayed an increased accumulation of neutrophils within the peritoneal cavity compared with wild-type control mice. These mice also displayed decreased survival in acute sepsis induced by cecum ligation and puncture, with increased neutrophil extravasation. The decreased survival and increased neutrophil accumulation were associated with the cleavage of Annexin A1, a powerful anti-inflammatory protein known to facilitate the resolution of inflammation. Furthermore, neutrophils from hPR3Tg mice displayed enhanced survival compare to WT controls and this may in part explain the increased neutrophil numbers observed during the later stages of inflammation. Taken together, our data suggest that human PR3 plays a proinflammatory role during acute inflammatory responses by affecting neutrophil accumulation, survival, and the resolution of inflammation. Our newly described transgenic mouse model could be used in the future to decipher the molecular mechanisms that contribute to PR3-dependent diseases and inflammation, including ANCA-associated vasculitis.