Amazon has begun allowing iPhone and Apple TV users to make in-app purchases and rent movies and shows from Amazon Prime.
The move is a reversal for Amazon which had forced Prime users to leave the app and go to Amazon's website via a browser to make purchases.
It is also a change for Apple which will allow Amazon to use its own payment system.
The changes apply to Amazon Prime users in the US, UK and Germany.
People using iPhones, iPads and iPod touches as well as Apple TVs began to see the changes on Wednesday.
A message from Amazon alerted users to the new feature when they opened the app.
"Browse, rent, or buy new release movies, popular TV shows, and more - now within the app," it read.
Prior to the change users of iOS or tvOS could only watch shows or films they had purchased directly from Amazon's website or on another device such as an Android phone or Amazon's Fire TV. If an Apple user wanted to buy a video from Prime they had to complete the transaction on Amazon's website.
The change is also significant for Apple because it means Amazon will be able to use its own payment system.
Apple typically charges a 30% commission for in-app purchases on its iOS and requires those apps to use Apple's payment system.
Allowing Amazon to use its own payment system means Amazon will avoid this charge.
Apple has said it made exceptions for "qualifying premium video entertainment apps". Those apps include Prime Video, Atlice One and Canal+.
Other companies have argued Apple's 30% charges are unfair
Spotify filed a complaint with the European regulators about the charge. The music streaming site referred to the 30% fee as a tax and said it would be forced to artificially inflate its prices as a result.