BuzzFeed’s chief marketing and chief creative officer, Frank Cooper, is leaving after a tenure of about 18 months, the digital media company said Monday.

Mr. Cooper has overseen BuzzFeed’s creative services team and worked with marketing executives and advertising agencies to create sponsored content that runs across BuzzFeed’s properties. He was previously a marketing executive at PepsiCo Inc. and AOL.

“We wish Frank the best,” a BuzzFeed spokeswoman said.

Mr. Cooper’s exit comes amid a relatively uncertain period for BuzzFeed. The company recently raised $200 million from Comcast Corp.’s NBCUniversal, a sum that doubled the TV giant’s investment in the company.

But the new investment gave BuzzFeed a post-money valuation of about $1.7 billion, according to people familiar with the matter, meaning that BuzzFeed’s valuation was essentially unchanged from NBCU’s first investment last year.

BuzzFeed missed its revenue projection for 2015 by about 20% but was on track this year to meet its new target, a person familiar with the situation has said.

Mr. Cooper reported to Greg Coleman, who leads BuzzFeed’s ad sales efforts.

BuzzFeed, like many other high-profile digital media outlets, must live up to high expectations after raising significant sums in recent years from investors drawn by their rapid growth. The challenge is to keep up that expansion in an online ad world where an array of publishers, not to mention tech titans Facebook and Google, are after the same pot of ad dollars.

BuzzFeed was among the first digital media companies to make a big bet on creating sponsored content, as brands such as Purina, Taco Bell and General Electric worked with the company’s team of viral specialists to fashion “listicles” and quizzes. In search of new streams of revenue, BuzzFeed and other digital media companies have been pouring resources into creating more video content for themselves and on behalf of brands.

The company also has high hopes for developing television and movie projects, and it has a film in the works based on a series of viral stories about a stolen iPhone.

Write to Steven Perlberg at steven.perlberg@wsj.com