The problem, which occurred between 09:30 BST and 14:00 BST yesterday (July 27th), led to users being unable to log in to check their personal banking details.
A message on the bank's website explained that it was experiencing "technical problems" and advised customers to try again later.
However, a spokesman for Barclays told the Register that the issue was fixed within a few hours.
"We had a short-term hardware problem which interrupted service but we are now starting to return to normal," he remarked.
The issue is believed to have been caused by a high volume of demand and follows a similar outage that occurred last month.
Barclays recently unveiled a redesigned version of its internet banking service, which offers improved navigation for users.
Figures from the bank show that it has over three million online banking customers, with an average of one million using the service every day.