B of A customers quickly vented their frustration over the shutdown on social media.
"Website is down and so is phone line???? That's terrible," said another customer over Facebook.
The banking giant said in a tweet that it was trying to restore service, but did not disclose what caused the problem, saying only that people may be "experiencing issues" accessing their account information.
By mid-afternoon, a B of A spokesman told CBS News the site was up and running again.
An internal system problem appears to be responsible for the shutdown, the company said without releasing additional details.