A new dollar-sign icon in the Messenger app for iOS, Android and desktop will connect users to a system that transfers money between Messenger accounts linked to US-issued debit cards.
The money will be available to the recipient within three days, the company said.
Industry watchers had been expecting Facebook to add electronic payments to Messenger since David Marcus, the former chief of online payment pioneer PayPal, took the helm of the instant messaging service in 2014.
Facebook is only the latest major tech company to focus on ways to move real money in the virtual world. Apple introduced Apple Pay in October to allow payments to stores using its devices.
But for now, Facebook's Messenger is targeting person-to-person payments rather than businesses, much like IM rivals Snapchat's pay-through-text service Snapcash, launched in November.