The companies said they expect the deal, which still needs to win regulatory approval and clear other conditions, will close by the end of this year.
Bakish said: "Today marks an important day for CBS and Viacom, as we unite our complementary assets and capabilities and become one of only a few companies with the breadth and depth of content and reach to shape the future of our industry".
Taking a page from the now Fox-expanded Disney book, new ViacomCBS kingpin Bob Bakish made very clear just now on today's investor call, Star Trek and the Mission Impossible franchises have significant potential to leverage "across all the companies' platforms".
Viacom owns Paramount Pictures and pay TV channels such as Comedy Central, MTV and BET, while CBS has a broadcast network, television stations, Showtime and a stake in The CW over-the-air network. Disney's is almost $245 billion and Netflix is at $136 billion.More news: Struggling Phillies bring back Charlie Manuel as hitting coach
CBS and Viacom said a merged company would be in a better position to accelerate a "direct-to-consumer" strategy - industry jargon for streaming services that don't involve any traditional TV distributor like a cable company. Bringing the two companies back together has always been a goal of Shari Redstone, who controls the company with Sumner, the aging family patriarch who has faced numerous health issues. Shari Redstone - who heads National Amusements, the majority shareholders of both CBS and Viacom - has been pushing for the companies to reunite for years. Joe Ianniello, who had been president and acting chief executive at CBS, will now be chairman and chief executive of the company's CBS division.
The companies said in a press release that they agreed to an all-stock merger that would combine the largest US television business with a major Hollywood studio in Paramount Pictures and other businesses that "accelerate CBS and Viacom's ability to deliver an array of compelling content to important and diverse audiences across both traditional and emerging platforms around the world".
Moody's media analyst Neil Begley said the biggest question will be whether the new company will focus on its subscription-based streaming services such as CBS All Access and Showtime or ad-supported ones like Pluto TV, or keep doing both.
CBS and Viacom have ties that go back to the 1970s.
But over time, the two companies' fates were reversed. A merger was adamantly opposed by Leslie Moonves, the former powerful chair of CBS who was brought down in a sexual harassment scandal previous year.More news: Joshua Ruiz II latest sport event to head to Saudi Arabia
Shari Redstone will become the new board chair of the combined ViacomCBS Inc.
"We would want to look at something after that to. develop more scale as we move forward", Redstone said at The Information's Women in Tech, Media and Finance conference in June.
The stocks of CBS and Viacom both rose less than 2% in afternoon trading Tuesday, a reflection of Wall Street having anticipated this deal, especially in recent days.
Under the deal's terms, Viacom shareholders would receive about a 0.6 share of CBS stock in exchange for 1 share of Viacom stock.More news: Perseids Meteor Shower To Peak Tonight For People Across Globe