In addition to Ackman, Pershing Square has nominated Veronica Hagen, the retired chief executive of Polymer Group, and Paul Unruh, a retired executive of Bechtel Group. They will be formally introduced at ADP's upcoming annual shareholder meeting.
ADP revealed Friday that Pershing had taken an 8 percent stake in the company, mostly in derivatives, and had asked to nominate a slate of five directors and remove ADP CEO Carlos Rodriguez, moves the company said it rejected. Later in the day, Ackman told CNBC he only intended to nominate a minority slate.
"We are pleased to nominate such superb independent directors to the Board of ADP who will bring relevant skills, expertise and judgment to assist the Board in achieving ADP's maximum potential," Ackman said in a statement on Monday.
In a statement, ADP said it is open to "constructive input" from its shareholders. The company said it will evaluate the nominees as it would any others. However, ADP said its 10-member board already has "the right balance of leadership continuity and fresh perspectives."
"The Board is always open to good ideas regardless of their source and reiterates the invitation it made to Mr. Ackman last week to present his ideas to the full Board on how 'to improve ADP's operations, profitability and competitive position,"' ADP said in a statement.
Pershing Square, an activist hedge fund, will not seek to oust Rodriguez, Reuters reported Monday, citing a source. It will work with ADP's management as long as it is open to making significant changes, the source added.
Pershing Square will hold a public webcast on Aug. 17 during which it will present its research on ADP.