Provided is a method in a wireless mobile terminal for inputting characters. The method includes computing a probability value for each character which may be entered after a user inputs a particular character from among characters assigned to each button on a key input section by pressing a button and, storing the probability value in a memory of the mobile terminal, the probability value being based on a detection frequency of each character to be detected after a particular character in preset words. A character, as a first input character, having been inputted by the user according to the number of times a first button has been pressed in character input mode, based on a first character arrangement preset on the first button, is displayed on a display section. The probability value for each character which is probable to be entered after the first input character, among characters assigned to all buttons of the key input section is read from the database, and a second character arrangement in the order of probability values for the characters assigned to each button is then determined. A character inputted by the user according to the pressing number of a second button, based on a second character arrangement preset on the second button is displayed as a second input character.