Under the deal, Turner's TBS and TNT will work with Mashable to co-develop and distribute video content and team on cross-platform ad sales packages. Kevin Reilly, chief creative officer for Turner Entertainment and president of TBS and TNT, will join Mashable's board. Mashable already counted Time Warner Investments among its backers.

'Just as we are redefining these networks and continue to innovate beyond the traditional television universe, Mashable is redefining digital storytelling, making us ideal partners in today's rapidly evolving media ecosystem,' Reilly said in a statement. 'We're confident our partnership will increase the cultural relevance of Turner and Mashable content across all of our platforms.'

The investment by Time Warner-owned Turner is the latest instance of big media companies pairing up with digital upstarts. Such pacts have included NBCUniversal's stakes in BuzzFeed and Vox Media; Vice Media's backing from Disney, A+E Networks and 21st Century Fox; and Disney's acquisition of multichannel network Maker Studios.

Mashable's Series C round brings it to a total of $46 million raised to date, after $17 million last year led by Time Warner Investments and $14 million in 2014 Series A led by Updata Partners. The latest funding also included participation from previous investors Time Warner Investments, Updata Partners, David Jones and Mike Lazerow, along with R&R Venture Partners, a fund created by Dick Parsons and Ronald Lauder.

Mashable declined to comment on its current valuation. The latest funding is an up round, according to sources.

New York-based Mashable said it will use the new funding to expand video production across all platforms including linear TV, as well as invest in its technology, data and advertising platforms.

Mashable's commercial partnership with Turner will let the two companies collaborate on programming, advertising and technology. Early collaborations will include developing new programming ideas and franchises using Mashable Velocity, a prediction and tracking tool; distributing select Turner programming to Mashable's digital audience; and pitching joint advertising-sales packages.

'Turner, home to the top-rated cable networks, is the perfect partner to bring the best of tech and digital culture to TV in fresh ways,' said Pete Cashmore, CEO and founder of Mashable.

Last June, Mashable launched Mashable Studios, with the mission of creating serialized video programming as well as branded entertainment for the company's website, social networks, television partners and OTT platforms.