NBC Universal invested $500 million in Snap Inc. on Thursday as part of the social-media company's initial public offering.

"This is a significant milestone in our growing partnership with Snap, and we look forward to participating in Snap's success as an investor and continuing to work closely with them for years to come," NBCU CEO Steve Burke said in a note to employees on Friday.

NBCU bought shares of Snap at $17 a share before they traded on the open market. After trading open, shares soared to $25 a share.

For marketers, the investment likely means expanded opportunities to buy against NBC content on the app, where young people are congregating even as they drift away from traditional TV.

NBCU struck a deal with Snapchat in August to bring shows like "Saturday Night Live" and "The Voice" to the social platform. During the 2016 Summer Olympics in Rio, NBCU produced content with BuzzFeed that ran on a pop-up Discover channel.

Mr. Burke said the company plans to launch more Snapchat shows with additional brands in the coming weeks.

NBCU has been investing in digital media companies. To date, the Comcast-owned media behemoth has invested $400 million in Buzzfeed and $200 million in Vox. It also recently acquired SportsEngine, a digital business that manages youth sports online and through its acquisition of DreamWorks, NBCU became a majority owner of Awesomeness TV.

Mr. Burke said its investment in Snap build on the company's "strategy to drive digital growth for our business, both organically and through investments and acquisitions."

In total, Mr. Burke said NBCU has invested over $1.5 billion in digital businesses over the last 18 months.