Under Armour will outfit all Major League Baseball players beginning in 2020 under an agreement reached with the league — the Baltimore brand’s first such partnership with a major American professional league.

The owners have approved the switch from Majestic Athletic to Under Armour, according to two sources with knowledge of the agreement.

The agreement hasn’t been announced. Under Armour representatives did not immediately return calls seeking comment.

Under Armour had been looking to make inroads with MLB, which partners with many sporting goods and apparel companies.

Rawlings makes the baseballs used in games, Majestic Athletic makes the uniforms, New Era Cap Co. makes the caps and Schutt Sports makes the bases. Nike is MLB’s supplier of the baseball undershirts known as base layers.

Under Armour produces some of the cleats, compression sleeves and batting gloves used by players. The company also makes a share of the catchers’ gear, an important marketing tool because catchers and their equipment brands appear so often on camera when games are televised.

“This is a major signal from Under Armour that they’re ready to play with the big boys,” said T.J. Brightman, president of Bel Air-based A. Bright Idea Advertising and Public Relations.

Majestic extended its MLB partnership last year through 2019. It could not immediately be determined if Majestic sought to continue the agreement or which other companies might have competed against Under Armour. Majestic officials couldn’t be reached Monday night at the company’s offices in North Carolina.

Major League Baseball divides its exclusive and shared licenses and supplier agreements among many corporate players. Marketing professionals say that doing so leads to more product choices and maximizes profits.

To date, Under Armour has gained attention in the sport by signing individual players to use and market its products.

The company signed Washington Nationals outfielder Bryce Harper, one of the sport’s marquee players, to an endorsement deal in 2011, when he was still in the minor leagues.

It has also signed Clayton Kershaw, the Los Angeles Dodgers’ star pitcher.

“Team sports are a pillar of our business, and baseball is an important player,” Peter Murray, vice president of global brand and sports marketing at Under Armour, said as the current baseball season began.

“We are always looking to explore a deeper relationship with the league and new rights opportunities.”

Howe Burch, president of TBC Advertising in Baltimore, said the MLB deal “represents a very big opportunity for Under Armour. Their origins are in team sports, and this gets them on the uniforms of one of the few professional sports leagues in the U.S.”

Burch noted that the brand already has many MLB players under contract who wear Under Armour cleats and catchers’ gear.

“This only enhances that presence,” Burch said. “It makes a lot of sense. It’s right in their wheelhouse.”

Majestic, meanwhile, “really has very little brand awareness and brand presence,” he said.

Brightman, a former vice president of corporate sales and sponsorship for the Baltimore Orioles, said the deal could help lure additional star players in the league to Under Armour endorsement deals.

Major League Baseball stands to benefit, too, by affiliating with a brand with strong recognition and customer loyalty, Brightman said.

The league is “always looking to get younger, to grow their fan base,” he said. “Under Armour is certainly cool with that millennial generation, whereas a company like Majestic has less brand recognition.”

While it’s too early to tell how or if uniform designs might change, he said, it’s possible that some teams, especially small-market teams, might be more open to new looks the brand might propose.

“This gives an opportunity to have uniforms stand out and sell more jerseys,” he said. “There are a lot of wins here.”

Such licensing agreements can represent hundreds of millions of dollars a year and stretch over the long term, Burch said.

The company made a push last summer to be the NBA’s uniform provider starting next year, but lost out to Nike. In football, Under Armour outfits players at the annual NFL combine for top prospects. But Nike makes the jerseys used in games.