A facial and neck muscle exercising device for positioning against opposite corners of a person's mouth at the opening thereof to strengthen and tone facial and neck muscles. The exercising device includes a pair of mouth spreading arms each having an elongate slide member and an end member contoured to engage the opposite corners of the person's mouth. The slide members are slidably connected together longitudinally and an arm retaining device connected thereto controls sliding movement and resistance of the mouth spreading arms. Versions of the arm retaining device elastically bias the end members against the corners of the person's mouth in an adjustable manner, allow adjustment of the length or range of motion of the exercising device, retain the exercising device at a fixed length, or a combination thereof.