An activist investor with a track record of shaking up large companies has taken a stake in Comcast Corp., arguing that the Philadelphia-based media giant should be more valuable.

Trian Fund Management has accumulated about 20 million shares in Comcast, or roughly a 0.4% stake in the company. Comcast has about 4.6 billion total outstanding shares and a market value of about $210 billion.

“Trian believes Comcast’s stock is undervalued,” a Trian spokesperson said. “We have recently begun what we believe are constructive discussions with Comcast’s management team and look forward to continuing those discussions.”

Wall Street appeared to welcome the move with shares climbing over 2% on the news Monday, though the stock ended the day down 1.3% at $44.68. Comcast’s stock price resumed climbing Tuesday, closing up 3.38% to $46.19. Trian’s venture into the company was first reported by the Wall Street Journal on Monday.

Comcast declined comment.

CEO and billionaire Nelson Peltz founded Trian in 2005 along with chief investment officer Ed Garden, who is Peltz’s son-in-law, and Trian president Peter May. The $10 billion-asset investment firm often pushes for change to deliver more cash to investors, such as cutting costs or selling business units. New York-based Trian has notably targeted giants Procter & Gamble, General Electric, and Wilmington-based DuPont with mixed results. Trian’s portfolio also includes stakes in burger chain Wendy’s and food maker Mondelez International.

Trian hasn’t publicly released demands of Comcast, but pursuing changes at the 57-year-old company could be a tall order. Comcast chairman and CEO Brian Roberts controls roughly one-third of shareholder votes at the company, which was founded in 1963 by his father, Ralph Roberts. Comcast’s stock hit an all-time high of $47.74 in January and shares have recovered to near that price after dropping during the coronavirus pandemic.

Activist investors are less likely to take on family-controlled companies such as Comcast than non-family companies because it’s harder to gain a big enough stake to force change, said Emilie Feldman, an associate professor of management at Wharton.

Yet, activist investors can create more value for those companies than for the equivalent non-family company, she added. Activists won’t challenge family-controlled companies just “for a single."

“They’re really going to only invest in companies that they think they can swing for the fences and hit the home run, and kind of really generate that value creation,” she said.

Over the last decade, Comcast has taken its media business global, acquiring NBCUniversal in 2011 and the British pay-TV service Sky in 2018. The company’s broadband business has boomed even as consumers cut cable TV, propelling profits up 11.3% last year to $13.1 billion.

Comcast’s diverse portfolio includes cable TV, internet, film, theme parks, broadcast television, cable channels, and Peacock, a new streaming service. It also owns the Wells Fargo Center arena and Philadelphia Flyers hockey team.

During a Goldman Sachs investors conference last week, Roberts said Comcast was where other media companies want to be, where media and tech converge, thanks to its investments in broadband internet.

“If you look at the big tech companies, they’re all about now getting into media. If you look at the media companies, they’re trying to use new technologies,” Roberts said Sept. 15. “Broadband is really the enabler. And the best thing for Comcast is we’re there. We saw this coming.”

Some analysts have been more skeptical. Craig Moffett, of the New York research firm MoffettNathanson, said in July that “Comcast is still woefully undervalued.” Following the company’s second-quarter earnings, Moffett noted that Comcast’s cable business has performed well while its NBCUniversal and Sky units have struggled.

“Short of separating the businesses into two, which we have no reason to expect, we’re still not quite sure what it will take for the valuation gap to close,” he wrote at the time.

Trian has a reputation for being less aggressive than other activist hedge funds, by not being as public with its demands or as “harsh” with some of the changes it seeks, Feldman said.

Peltz has built Trian into one of Wall Street’s busiest activist investment firms, targeting companies he said had too much cash, too many executive perks and unproductive expenses, and not enough sales growth or profits. He distinguished himself from earlier corporate raiders by calling his approach “constructive,” and seeking to work with management. But he can be bruising and has been known to launch public attacks designed to build allies with mutual funds, pension funds, and other institutional investors whose support he would need against entrenched CEOs.

In 2013, Peltz told the directors of the DuPont Co.. that he had accumulated a 2.2% stake in the Wilmington-based chemical giant. The inventor of nylon, Kevlar, and many other materials, DuPont had a share price that trailed other Dow Jones industrials stocks from the 1990s into the 2010s.

Peltz urged DuPont to cut costs, streamline its product pipeline, and improve corporate governance.

He put pressure on DuPont’s CEO, Ellen Kullman, who left in late 2015, and helped negotiate a plan to merge the company with Dow Chemical before splitting the merged firm into smaller, more focused companies. Still, DuPont shares failed to rise much, even after the merger. In 2017, Trian sold its shares.

Peltz knows at least one Comcast director, Ed Breen, the DuPont CEO, who got that job thanks to Peltz’s pressure on the company five years ago, replacing Kullman.