Dimon was a hero of the 2008 Wall Street crash for keeping his bank in good shape, but JPMorgan's huge loss this year brought Dimon to a senate hearing.
Dimon admitted the minimum loss is $2 billion.
"We will lose some of our shareholders' money - and for that, we feel terrible - but no client, customer or taxpayer money was impacted by this event," he said.
Dimon testified the crisis came when top staffers in London tried new ways to reduce risk, a hedge.
Dimon admitted on cnbc recently that he got a warning memo, but admitted he thought it was "insignificant" at the time.
Banking critics say the JPMorgan Chase scandal is more of the same Wall Street behavior that led to the 2008 crash.
"We've got the same big too big to fail Wall Street banks engaging in the same high risk investment and trading, that risk, yet another failure and another bailout by the American taxpayers and that's not acceptable," says Dennis Kelleher, president of Better Markets, Inc.
Still, Dimon argued against more regulation.
"We have widest, deepest, best capital markets in the world. It would be shame to shed that out of anger," he said.
Investors liked Jamie Dimon's performance on Capitol Hill.
JPMorgan Chase stock shot up about 3% after his testimony.