The 58-year-old socialist leader needed "corrective measures" that stopped the bleeding, Information Minister Ernesto Villegas said in a statement.
"This process of recovery will take time because of the complexity of the operation," Villegas said in a broadcast on national television. "The patient is in a progressive and favorable recovery of normal vital signs."
He did not provide further details.
The ashen faces of cabinet ministers and somber tone of the terse official statements since the operation appear to suggest top government officials are preparing for the worst.
Chavez won re-election by a big margin in October and is due to start a new six-year term on Jan. 10. According to the constitution, if he is unable to do so, a new election must be held within 30 days.
The president has refused to divulge the details of the cancer diagnosed in mid-2011 and has twice declared he was completely cured - only to later undergo more surgery.