The Royal Bank of Scotland plans to equip all 100,000 of its staff with the business version of Facebook by the end of next year.
It started piloting Facebook at Work in July, and today said it would roll out the product to an initial 30,000 employees by the end of March next year, with the remainder to be on the platform by the end of 2016.
RBS claims to be the first bank in the world to implement the tool at such scale.
Facebook At Work launched in January this year and is intended to allow co-workers to interact as others do on the consumer platform.
It offers a similar design to the consumer version and allows employees to post, like and comment on photos and status updates; create groups and events; and send private messages to work "friends".
The tool competes squarely with enterprise collaboration platforms like Microsoft's Yammer, Salesforce's Chatter, Atlassian's Hipchat, and Slack.
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RBS said the software would help its staff communicate faster and more effectively.
"Given how many people already use Facebook in their every day lives, it was picked up quickly by those on the pilot, with minimal training needed," the bank said in a statement.
The pilot showed that employees using Facebook At Work were answering customer questions faster, coming up with better ideas for projects, and updating colleagues in a more engaging manner, the bank said.
Work profiles are separate to an employee's personal Facebook account. Information shared on the platform is only accessible to other RBS workers.
Staff will also be able to access the platform on smartphones and tablet devices.