The BT deal with HBO Home Entertainment gives the telco several of the premium cablers dramas for its download store.
Other titles include all seasons of Entourage and True Detective.
Game of Thrones seasons one to four are available. BT said new HBO titles will be added through the year.
The HBO fare can be viewed on BT TV’s set top boxes and smartphones, tablets or PCs.
Alex Green, director of BT TV, said: “We believe customers will increasingly choose digital ownership given its freedom and flexibility and the ability to create your own personal movie library. Meanwhile our TV Everywhere service allows families to enjoy some of their favourite channels around the home and on the move.”