Disney's streaming service, which is launching next week and had said it will be ad-free, will carry a one-time promotion for the cable channel Starz.

Disney will show the promotion after the sign-up process, a Disney spokesperson told CNBC on Tuesday. Subscribers after the Nov. 12 launch will see the promotion only once. Those who subscribe before the launch will not see the promotion, and no subscribers will see any ads while watching programs, the spokesperson said.

The promotion highlights the complicated world of licensing as traditional media companies like Disney, AT&T's WarnerMedia and Comcast's NBCUniversal prepare their respective streaming services with their own shows and movies. For example, earlier this year, NBCUniversal paid $100 million for the rights to "The Office," which will leave Netflix in 2021, underscoring the investment these companies are making to build a catalog of content on their services to woo subscribers.

Disney has in the past tapped revenue by signing costly licensing deals with TV channels and streaming services such as Netflix and Starz that allows those companies to show Disney-made movies. The Disney movies licensed to Starz includes "Star Wars: The Force Awakens," which will be available for streaming when Disney+ launches.

Representatives from Starz declined to comment.

Disney+ will cost $6.99 per month or $69.99 per year. Subscribers will also have the option to bundle Disney+, ESPN+ and ad-supported Hulu for $12.99 a month.

The arrangement with Starz was first reported by The Verge.

Disclosure: Comcast owns NBCUniversal, the parent company of CNBC.

Correction: An earlier version misstated where the promo for Starz will appear on Disney+. It will show one time after a subscriber completes the sign-up process.