Bill Ackman's Pershing Square has taken a stake in Lowe's, a source tells CNBC.

Ackman's new stake in the home improvement retailer was first reported by Dow Jones.

The hedge fund manager revealed the approximately $1 billion sized position at a Kirkland & Ellis conference in New York Wednesday, a source tells CNBC.

Ackman said he supports the company's incoming chief executive Marvin Ellison at the conference, according to the Dow Jones report. The hedge fund manager also said he agrees with activist investor D.E. Shaw's position that Lowe's needs to do more to catch up with its competitor Home Depot.

The CNBC source said Ackman is not currently seeking a board seat at Lowe's.

Lowe's shares are up 9 percent Wednesday after the retailer reported its first-quarter financial results. The company has a market value of nearly $78 billion.

It has been a difficult few years for Pershing Square's investors. The hedge fund's returns fell 4 percent in 2017, dropped 13.5 percent in 2016 and declined 20.5 percent in 2015, according to its Pershing Square Holdings website.

The fund is up 0.1 percent this year through May 15.

Lowe's sent the following statement when asked for comment:

"We are aware of reports that Pershing Square has invested in Lowe's. The Lowe's Board of Directors and management team remain committed to creating value for all shareholders, and will continue to take actions to achieve this objective."

— CNBC's Leslie Picker contributed to this story.