He and US Ambassador Philip D. Murphy took part in the memorial service at the American Church to mark the 10th anniversary of the attacks. Other guests included Foreign Minister Guido Westerwelle, former Chancellor Gerhard Schröder and Interior Minister Hans-Peter Friedrich.
Those attending the service held a minute of silence in memory of the 3,000 victims of the attacks by radical Islamic terrorists on New York and Washington.
Wulff will also take part in a memorial event in Munich in the afternoon, which will include a live broadcast from Ground Zero in New York.
A memorial event is also planned to take place at Berlin's historic Brandenburg Gate, at which a young people from different religious communities will join together for discussion, prayers and music.
A minute of silence is to be held throughout the city at 2:46 p.m. local time, to mark the moment that the first plane hit the World Trade Centre in New York 10 years ago.
Another memorial service is being held at the Berlin Cathedral at 6 p.m.