A cleaner head for a vacuum cleaner including an agitator in the form of a brush bar, the brush bar including a plurality of radially extending bristles and a sealing material disposed between the bristles. The sealing material extends over substantially the entire circumferential and axial extent of the regions of the brush bar between the bristles. The cleaner head further includes a housing defining a chamber which at least partially surrounds the brush bar, a dirty air inlet in a lower part of the chamber and a front opening that exposes the brush bar at the front of the housing. The brush bar is supported for rotation with respect to the housing and arranged in the chamber such that the brush bar seals against the housing thereby restricting flow of air through the front opening.