A spokesperson for the bank today confirmed to iTnews that the initiative went live on March 7.
The service sends personal internet banking customers a six-digit code via SMS, which needs to be entered on the website to enable a transaction or change to proceed.
Previously, two-factor authentication was available only to Westpac business customers, mainly in the form of a token.
"This rollout to personal customers is part of our ongoing commitment to providing customers with additional security protection and was always part of our overall security consideration," a Westpac spokesperson told iTnews.
"We have already advised certain customers - in particular those who have previously been victims of fraud and customers who request to change their internet banking daily transaction limit - about the service and how to register".
Apart from increased security, Westpac is touting benefits including an increased daily limit up to $10,000 with the ability to set it online, and alerts to unauthorised activity.
Westpac joins CBA which this week also announced a major expansion of its own SMS authentication system for personal internet banking customers.