Abstract: A barrier device for sleep positioning including, in one embodiment, an elongated body to be placed atop a head-contacting surface of a pillow so as to define generally a boundary between a left side and a right side of the pillow, and at least one attachment device for securing the barrier device to the pillow. The elongated body has top and bottom ends and includes a pair of outwardly-projecting portions located at left and right sides of the elongated body near the bottom end. Each outwardly-projecting portion has an outer curvature substantially the same as and abutting at least a portion of the back of the head and/or neck of a user lying on the user's side with the user's head resting on one of the sides of the pillow.