An inertial particle separator (IPS) for a gas turbine engine, has: inner and outer walls extending about a central axis, an inlet defined between the inner and outer walls and oriented axially; swirling vanes extending at least radially between the inner and outer walls and circumferentially distributed around the central axis, the swirling vanes configured for inducing a circumferential component in an airflow flowing between the swirling vanes; a plenum between the inner and outer walls downstream of the swirling vanes, the plenum circumferentially extending about the central axis, the outer wall converging toward the central axis in a direction of the airflow; and a splitter radially between the inner and outer walls downstream of the plenum and circumferentially extending around the central axis, a particle outlet radially between the splitter and the outer wall, an air outlet radially between the inner wall and the splitter.