Agencies:

* United States Citizenship and Immigration Services – Processes citizenship, residency, and asylum requests from foreigners
* U.S. Customs and Border Protection – Staff border checkpoints, collect tariffs, and patrol the border
* U.S. Immigration and Customs Enforcement – Long-term investigations of border violations
o Federal Protective Service – Law enforcement and security for federal buildings, properties, assets, and interests
* Transportation Security Administration – Responsible for aviation security (domestic and international, most notably conducting passenger screenings at airports), as well as land and water transportation security
* United States Coast Guard – Maritime security, national defense, maritime mobility, and protection of natural resources (assigned to Department of the Navy during times of war or at the president's direction)
* Federal Emergency Management Agency – Disaster preparedness, response, and recovery
* United States Secret Service – Protective services for important officials and protection of the U.S. currency

(Passports for U.S. Citizens are issued by the United States Department of State, not the Department of Homeland Security.)

Advisory groups:

* Homeland Security Advisory Council – State and local government, first responders, private sector, and academics
* National Infrastructure Advisory Council – Advises on security of public and private information systems
* Homeland Security Science and Technology Advisory Committee – Advise the Under Secretary for Science and Technology.
* Critical Infrastructure Partnership Advisory Council – Coordinate infrastructure protection with private sector and other levels of government
* Interagency Coordinating Council on Emergency Preparedness and Individuals with Disabilities
* Task Force on New Americans – "An inter-agency effort to help immigrants learn English, embrace the common core of American civic culture, and become fully American."

Other components:

* Domestic Nuclear Detection Office – Develop nuclear threat detection capabilities at all levels of government and in the private sector
* Federal Law Enforcement Training Center – Interagency law enforcement training facility
* National Protection and Programs Directorate - risk-reduction, encompassing both physical and virtual threats and their associated human elements
o National Communications System
* Directorate for Science and Technology – Research and development
* Directorate for Management – Responsible for internal budgets, accounting, performance monitoring, and human resources
* Office of Policy – Long-range policy planning and coordination
o Office of Immigration Statistics
* Office of Health Affairs – Medical preparedness
* Office of Intelligence and Analysis – Identify and assess threats based on intelligence from various agencies
* Office of Operations Coordination – Monitor domestic security situation on a daily basis, coordinate activities with state and local authorities and private sector infrastructure
* Office of the Secretary includes the Privacy Office, Office for Civil Rights and Civil Liberties, Office of Inspector General, Citizenship and Immigration Services Ombudsman, Office of Legislative Affairs, Office of the General Counsel, Office of Public Affairs, Office of Counternarcotics Enforcement (CNE), Office of the Executive Secretariat (ESEC), and the Military Advisor's Office.
* National Cyber Security Center