Shortly after the September 11, 2001 terrorist attacks, Lawlor joined the White House staff to help plan and coordinate the response as Senior Director for Protection and Prevention in the Office of Homeland Security. While in this position Lawlor was one of the chief creators of the legislation that created the Department of Homeland Security. When DHS was officially founded in March, 2003 Lawlor was named its first Chief of Staff, and he served until being succeeded by J. Duncan Campbell in October, 2003.