Users can earn 800 Microsoft Points for trying the service free of charge for one month, and a further 1600 Points for making a subsequent payment of £8.99.
Open to Xbox Live Gold members only, the promotion is available until January 31 through the NOW TV website.
The streaming service costs £8.99 a month for the first three months, after which users will be charged a monthly fee of £15.
According to the product description, NOW TV offers the latest movies 12 months before Lovefilm and Netflix, and also provides access to Sky's 11 movie channels.
NOW TV launched on the Xbox 360 in August, offering high-quality video streaming at 720i resolution.
Kinect for Xbox 360 owners are also able to use voice and gesture controls for the NOW TV app.
More content from Sky will be added to NOW TV over the coming months, including Sky Sports and a range of entertainment shows from channels such as Sky Atlantic and Sky1.