The new feature called #AmazonCart allows people to link their Twitter and Amazon accounts for in-app purchases.
"We know that discovering products and services on Twitter is a natural, and we always look for ways to make that easier for users," said Twitter spokesman Will Stickney in a statement.
"That's why we built this capability through our relationship with Amazon."
Terms of the deal were not announced.
Amazon made the announcement in a tweet, calling it "an exciting new way to add Amazon products to your cart, without leaving Twitter."
Amazon spokeswoman Julie Law, in a statement, explained the process:
"It's simple. When a customer discovers a tweet from their favorite artist, expert, brand, or friend with an Amazon.com product link, they simply add '#AmazonCart' to their reply on Twitter and the product is added to their Amazon.com Shopping Cart," she said.
"Customers who have not connected their Twitter and Amazon.com accounts will receive a reply tweet asking them to connect their accounts to enable the new feature."
The Amazon website explains the process, showing how Twitter users can select items, and then later go to the Amazon site for payment.
The service is available for customers of Amazon in the United States and in Britain, where it is called #AmazonBasket.
Some reports pointed out a potential privacy issue: that because tweets are mostly public, the Amazon purchases would likely be visible on Twitter.