The bank said the new online keypad, which replaces the old sign-in page, would tighten security for its 1.9 million Internet banking customers by removing the use of a keyboard to enter passwords.
Cybercriminals have devised ways of recording keystrokes entered on a Web page, and have in the past used this to capture online banking customers' passwords.
"The online keypad uses special technology to scramble Customer IDs and passwords and prevent those attempting fraud from capturing entered information," said Westpac head of channel and systems management, Paul Jennings.
Westpac claimed to be the first major bank to introduce the initiative, although keypads are already used by other industry players, such as ING.
Jennings said Westpac would continue to investigate further security initiatives for its online banking service.