Enron is expected to file for bankruptcy this week
According to figures on Enron's website, the bank is owed $126.1m (£89m) by the company.
The figure is less than press and market speculation had suggested.
Some rumours had pinned Barclays' exposure at as much as £300m.
The bank said Enron's collapse would not have any "material" effect on its business.
Nor, in a trading statement, did Barclays increase its bad debt provision from the £1.1bn it is already setting aside for the full year.
The bank pointed out that the "bald" $126.1m number did not take into account any hedging or syndicating of the risk with other lenders.
The news saw Barclays' shares tumble 81 pence, or 3.77%, by 1548 GMT to £20.69.
Barclays is not the worst hit. Abbey National has already admitted to being owed £115m, and is now expecting a £95m loss in the second six months of the year.
National Australia Bank, the owner of Yorkshire and Clydesdale Banks in the UK, is exposed to the tune of $200m (£141m).
Royal Bank of Scotland - the main focus aside from Barclays of speculation about loans in the hundreds of milllions of pounds - has yet to put a figure on its involvement.
Rapid demise
Enron is now seeking protection from its creditors under US bankruptcy law.
It was brought to the brink of collapse last week, when rival energy group Dynegy pulled out of a $8.4bn (£5.9bn) takeover deal.
Dynegy's withdrawal followed decisions by the three major rating agencies to cut Enron bonds to junk status, over concerns about firm's ability to repay debts, and on Friday the Standard & Poor's agency cut Enron's ratings yet again.
The company's European operations have already been placed into administration, and on Friday, Enron said it was cutting 1,100 jobs at its London energy trading centre.