The supermarket has already expanded the online entertainment section of its website with a new section selling books, DVDs, Blu-ray discs, CDs and video games – pitting it against the likes of Amazon and Play.com.
Before Christmas, the supermarket giant will start offering downloads of new music tracks and albums, as well as back catalogue titles.
The music downloads will be available at "competitive prices", says Sainsbury's, and will be compatible with all music libraries and MP3 players.
Films for purchase or download will follow, and a range of ebooks will be added early next year. Exact pricing to be confirmed.