The firm revealed it would be testing the button in the US with a "few small and medium-sized businesses", as it looks to help advertisers drive more sales through activity on Facebook.
The social network has also attempted to pre-empt privacy concerns by insisting that no credit or debit card information will be shared with other advertisers.
Facebook said in a blog post: "Today we’re beginning to test a new feature to help businesses drive sales through Facebook in News Feed and on Pages.
"With this feature, people on desktop or mobile can click the 'Buy' call-to-action button on ads and Page posts to purchase a product directly from a business, without leaving Facebook.
"We’ve built this feature with privacy in mind, and have taken steps to help make the payment experience safe and secure. None of the credit or debit card information people share with Facebook when completing a transaction will be shared with other advertisers, and people can select whether or not they’d like to save payment information for future purchases.
"The current test is limited to a few small and medium-sized businesses in the US. We’ll share more information as we gather feedback."
Facebook has been encouraging brands to sell directly through the social network for several years. In 2011, Marketing reported that Asos had become the first brand in Europe to allow users to buy its product range within its Facebook page.