Murtha spokesman Matt Mazonkey said the congressman, 77, was admitted to the hospital complaining about stomach pains, which were determined to be from a "gall bladder issue."
"He's currently resting and doing well," Mazonkey told Fox News.
The House Defense and State-Foreign Operations Appropriations subcommittees had planned a joint hearing Tuesday morning featuring Secretary of State Hillary Clinton and Defense Secretary Robert Gates, but that was postponed. The panel did not say that Murtha's absence was the reason for the delay.
Murtha is among a group of lawmakers who has suggested a war tax to pay for additional Afghan combat operations.
Fox News' Chad Pergram contributed to this report.