Abstract: In the representative embodiments described in the specification, a vertical sidewall sprinkler arrangement has a deflector supported from the junction of a pair of frame arms of the sprinkler and arranged to direct water in a generally horizontal direction. The deflector has a planar central portion substantially perpendicular to the sprinkler axis and extending in a direction parallel to the plane of the frame arms of the sprinkler on one side of the sprinkler axis; a first angled portion on the opposite side of the sprinkler axis, bent at an angle of about 50° from the planar central portion toward the sprinkler; and second and third angled portions extending outwardly from the planar central portion of the deflector and from the plane of the frame arms and bent toward the frame arms at an angle of at least 30° from the planar central portion.