The grand jury has been investigating Edwards, a former North Carolina senator, 2004 Democratic candidate for vice president, and 2008 presidential candidate, for more than a year.
He has denied any wrongdoing.
Former spokeswoman Jennifer Palmieri spent about an hour at the Raleigh courthouse on Thursday. Former deputy campaign manager Jonathan Prince spent four hours. Neither commented when leaving.
Palmieri also was a confidant of Elizabeth Edwards. She now works at the Center for American Progress think tank. Prince was a close aide to Edwards for both presidential campaigns.
According to sources, prosecutors are focused on the possible misuse of campaign contributions. They want to know about the arrangement to conceal the affair and the baby John Edwards had with his mistress, Rielle Hunter.
Sources say prosecutors are gathering information about the people who donated money to help Edwards' former aide Andrew Young, his wife, and Hunter live a life on the run.
Both Hunter and Young have testified before the grand jury.
Hunter worked for Edwards' political action committee in 2006, shooting behind-the-scenes video as the Democrat prepared to launch his White House campaign. The committee paid her video production firm $100,000 that year and then another $14,000 later on in what a senior campaign official described as a payment for leftover footage.
Young has said he was tasked with taking care of Hunter both during the campaign and after. He described receiving hundreds of thousands of dollars from Edwards supporters.
Also Thursday, ABC11's Chopper 11 HD filmed a private plane - reportedly with members of the Mellon family on board - arriving at RDU.
Young has said that some of the money came from Bunny Mellon, the wealthy widow of banking heir Paul Mellon and Edwards campaign finance leader Fred Baron, who died last year.
Edwards has largely been in seclusion since admitting two years ago that he had an affair with Hunter. He publicly admitted for the first time earlier this year he fathered her child. John and Elizabeth Edwards have separated after more than 30 years of marriage.
The ABC11 I-Team reported Wednesday that the Edwards campaign account is still flush with nearly four million dollars - and according to FEC filings - is spending between 50 and 90-thousand dollars every month.