They're also trying to fend off chains such as Chipotle and Panera, which are reshaping customer expectations about food and prices.
Wendy's spokesman Denny Lynch said the company doesn't offer delivery in the U.S., although he noted some small franchisees might have it. A McDonald's representative wasn't immediately available to say whether the chain offers delivery.
Whether Burger King's delivery service will prove popular enough to pick off customers from its rivals remains to be seen, with the service still fairly limited for now.
Burger King says about 20 restaurants will participate in the Chicago and Los Angeles area, and 15 in the San Francisco Bay area. The chain has about 13,000 restaurants globally, with about 7,500 in North America.
Customers can place orders online or by phone between 11 a.m. and 10 p.m. and orders must be a minimum of $10.
A representative for Burger King Worldwide Inc. said delivery boosts sales at restaurants where it's available but declined to provide further details. The company is looking to expand delivery to more locations based on demand.