Warner Bros Discovery shares were up 0.8% at $24.62, while AT&T stock climbed 2% to $18.62 before the bell.
AT&T and Discovery set out to create a standalone media business in May last year and the deal closed on Friday, with the new business housing channels including HBO, CNN and the Discovery Channel as well as franchises like "Batman" and "Harry Potter".
The company, which also owns streaming services HBO Max and Discovery+, faces stiff competition from the likes of Netflix and Walt Disney Co's Disney+.
Warner Bros Discovery is led by long-time Discovery veteran David Zaslav, and the new leadership team, announced last week, comprises many of his lieutenants.
"We expect that Zaslav will use his experience to help Warner Bros. Discovery transition into a DTC (direct-to-consumer) powerhouse by focusing further investment in both content and the user experience, which has garnered complaints on both HBO Max and Discovery+," Morningstar analyst Neil Macker wrote in a note.
Analysts at MoffettNathanson also signaled rising interest rates as a concern for the stock, adding there are concerns about slowing DTC subscriber growth across the industry.
Meanwhile, AT&T can focus on its core business as the telecom major uses part of the proceeds to cut down debt.
J.P. Morgan said it was an attractive time to buy into AT&T.
"We see the stock as defensive and inexpensive with a high dividend yield of 6.0% and FCF (free cash flow) yield of 14.2% as long as the company can continue to deliver on its guidance and financial targets," the brokerage said.
(Reporting by Yuvraj Malik in Bengaluru; Editing by Devika Syamnath and Sriraj Kalluvila)