His Philadelphia defense lawyers, Robert Welsh and Catherine Recker, said they expected McCord to plead guilty to charges to be filed in Harrisburg "in the near future."
The disclosure was a bombshell for the 55-year-old Democrat from Montgomery County, who twice won statewide office and once was a contender for the governor's seat.
It came a day after McCord announced his resignation from the post he had held for six years. He said then that he planned to step down Feb. 12 and return to the private sector, where he made a fortune as a venture capitalist.
But those plans quickly crumbled amid reports that he was entangled in a federal criminal investigation.
His lawyers said McCord had not stolen or misused campaign funds, as some of those reports said. But neither they nor McCord, in his video statement, offered details on the accusations, the donors, or the crimes he plans to admit.
"I do hope over time, people will evaluate my service to the commonwealth and conclude I did serve them well and in good faith," McCord said. "But I know my improper efforts to raise campaign contributions will forever be a stain on my record."
Gov. Wolf called the news "a sad day for the Commonwealth of Pennsylvania and for Rob McCord's family."
The governor added: "This type of behavior leads to the erosion of the public's trust - it is simply unacceptable. I stand firm in my commitment to restore the public's trust in their government."
Added House Minority Leader Frank Dermody (D., Allegheny): "I am shocked and dismayed at this news from a man whose achievements in the private sector and in public office I admired. The apology and resignation are a necessary first step, but this betrayal of public trust is tremendously disappointing."
Wolf said he would move quickly to appoint a successor.
The state treasurer is responsible for safeguarding and managing the state's money. Aside from reviewing and processing payments for state agencies, the treasurer also is a key investor of state dollars.
The treasurer, elected every four years, also serves on several powerful boards, including the two major public-employee pension systems and the Delaware River Port Authority.
In announcing his resignation Thursday, McCord named Christopher J. Craig, his onetime chief counsel, to fulfill the treasurer's duties until Wolf fills the post.
Craig previously served as the chief Senate lawyer for State Sen. Vincent J. Fumo before Fumo's 2009 conviction on corruption charges. Craig issued a statement Friday saying it was difficult to watch McCord's tenure end as it did.
"As we await a new treasurer assuming office, the leadership team already in place is committed to ensuring the continuity of Treasury operations and to remaining good stewards of the public trust," he said.
McCord finished third in last year's Democratic primary, behind Wolf and Allyson Y. Schwartz.
Inquirer staff writer Craig R. McCoy contributed to this article.