NBCU and Vox Will Start Selling Ads on Each Other’s Sites

Comcast Corp.’s CMCSA -1.67% NBCUniversal agreed to make a $200 million strategic investment in the digital media company Vox Media in August. Now the partners are getting to the strategic part.

Starting this week, NBCU will run Vox’s custom ad products on its digital properties, and both companies’ sales teams will start selling packages to marketers that include these ads.

With this new initiative, dubbed Concert, Vox and NBCU say they are aiming high. For starters, it’s a scale play. The two companies are talking up their ability to run ads on roughly 20 sites, ranging from NBC.com to SyFy.com to TheVerge.com, which collectively reach over 150 million people a month, according to comScore data.

For example, an advertiser looking to target foodies might consider an ad buy that includes TV spots on NBC’s “Today,” commercials during various Bravo series and ads on Eater.com, said Linda Yaccarino, NBCUniversal’s chairman of advertising sales and client partnerships.

In addition, Vox and NBCU are talking up this collaboration as essentially the start of a premium, brand-friendly ad network—one that blends bold, high-impact creative with ads that work well on mobile devices and load fast. According to Jim Bankoff, chairman and chief executive of Vox Media, this approach is crucial as digital media companies angle for a bigger chunk of traditional marketers’ ad budgets while also trying to tamp down the rise of ad blocking.

“We see a real void in the market for quality ad building in digital,” he said. “The whole point of brand building is to build trust. It’s impossible to do that with ads that suck.”

Over time, Vox is hoping to get more big media partners to adopt its custom ads. NBCU’s minority investment last year valued Vox at about $1 billion, people familiar with the situation said at the time.

For this deal, besides better creative, a big focus will be helping advertisers apply their own data to target ads across a wide variety of properties, Mr. Bankoff said. That should theoretically help NBCU and Vox better compete with companies that specialize in data-driven, “programmatic” ads.

Ms. Yaccarino wouldn’t commit to what percentage of ad inventory on NBCU’s sites will feature Vox-built creative. But the goal is to find out which ads work best for advertisers, and to run more of them, she said.

“It’s a brand new product, but we want to evolve it and scale it as much as possible,” she said. “The idea here is these ads are big, bold and beautiful, and you don’t have to worry about fraud, and you don’t have to worry about viewability.”

Write to Mike Shields at mike.shields@wsj.com