The panel in North Carolina found him not guilty on one of six charges of misuse of campaign funds, but could not agree on the other five.
It is not clear if prosecutors will retry Mr Edwards on the other counts.
Mr Edwards, 58, denied using donor funds to hide his mistress’s pregnancy during his 2008 run for the presidency.
While the cover-up of the affair was going on, Mr Edwards’s wife was fighting breast cancer.
Speaking outside the court, Mr Edwards said he had not done anything illegal but had done an “awful, awful lot that was wrong”.
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