A keypad assembly for a portable radiotelephone and a method for controlling the keypad assembly. The keypad assembly includes: a printed circuit board having a plurality of metal domes; a keypad rubber disposed on the printed circuit board and having bosses formed integratedly on the positions corresponding to the respective metal domes; a sensing means disposed on the keypad rubber; and a key button part disposed on the sensing means, such that a touch screen function using the sensing means or a key button function electrically contacting the metal domes is selectively used according to the mode of the radiotelephone.