A seat assembly having a seat back and a support post for supporting a headrest. The seat back may have a cross member that may include a support post opening and a flexible arm that may have a barb. The flexible arm may flex between a latched position in which the barb may be disposed in a notch of the support post to inhibit movement of the support post and an unlatched position in which the barb may be spaced apart from the notch to permit removal of the support post from the support post opening.