Pfeiffer, 37, has worked for the president since Obama began his presidential campaign in 2007 and is his chief adviser, The New York Times reported Friday.
Amy Brundage, a White House spokeswoman, described Pfeiffer as "feeling better, listening to his doctors and focused on helping implement the president's very full domestic and foreign policy agenda."
Doctors have diagnosed him with high blood pressure.
Brundage said Pfeiffer fell ill during dinner at a Washington restaurant Sept. 4. He went to a hospital where he was evaluated overnight, but went to work the next day. Pfeiffer had a recurrence that day and was hospitalized for two days.
After his release Saturday, Pfeiffer returned to the White House to help prepare Chief of Staff Denis R. McDonough for his appearance on the Sunday talk shows.
Pfeiffer worked all this week, with his blood pressure monitored by White House doctors, The Hill reported.
He joined the White House staff as communications director and is now the assistant to the president and senior adviser.