Lautenberg spokesman Caley Gray said Monday that the New Jersey Democrat was feeling better and would be back for Senate votes on the budget expected later this week.
Lautenberg had missed several votes over the past two weeks after his doctor advised him not to travel.
He announced last month he would retire next year and not seek re-election.
Lautenberg was sick with the flu in late December and early January and missed several votes. He was diagnosed in February 2010 with B-cell lymphoma of the stomach and underwent chemotherapy treatments until he was declared in June 2010 to be free of cancer.