Major retailers including Best Buy, Amazon.com, RadioShack and Wal-Mart also will carry the smartphone and smartwatch.
Samsung unveiled the products on Wednesday. The smartwatch is designed to let users check messages with a glance at their wrists or have a conversation through a speaker phone.
The watch must be linked wirelessly with a smartphone to perform its full range of functions. It acts as an extension to the phone by discreetly alerting users to incoming messages and calls on its screen, which measures 1.63 inches (4.14 centimeters) diagonally.
AT&T said it will sell the phone for $299.99 with a new two-year agreement, or for $35 a month under its AT&T Next installment plan. It will begin shipping orders on October 1.
T-Mobile said it plans to sell the smartphone for $199.99 down with 24 monthly payments of $21. It's also selling the smartwatch for $299.99. US Cellular confirmed that it will start selling the phone next month, but didn't announce pricing.
The smartwatch will be available in jet black, oatmeal beige, rose gold, wild orange, lime green and mocha gray. The phone and the tablet will be available in jet black and classic white. Colors will vary by seller, Samsung said.