Promoting Antiterrorism Cooperation through Technology and Science Act, or PACTS Act - Amends the Homeland Security Act of 2002 to direct the Under Secretary for Science and Technology of the Department of Homeland Security (DHS) to establish the Science and Technology Homeland Security International Cooperative Programs Office (the Office).

Provides for the Office to be headed by a Director, who: (1) shall be selected by and shall report to the Under Secretary; and (2) may be an officer of DHS serving in another position.

Requires the Director to: (1) develop, in consultation with the Department of State, understandings or agreements that allow and support international cooperative activity in support of homeland security research, development, and comparative testing; (2) develop, in coordination with the Directorate of Science and Technology, the other components of DHS, and other federal agencies, strategic priorities for such activity; and (3) facilitate the planning, development, and implementation of international cooperative activity to address such priorities.

 Requires the Director to: (1) facilitate the matching of U.S. entities with non-U.S. entities that may partner in homeland security research activities; and (2) ensure that activities are coordinated with those of other relevant research agencies. Permits the Director to run projects jointly with other agencies.

Authorizes the Director to hold international homeland security technology workshops and conferences to improve contact among the international community of technology developers and to help establish direction for future technology goals.

Authorizes the Under Secretary to carry out international cooperative activities to support specified responsibilities of the Under Secretary, including through the award of grants and the entering into of cooperative agreements or contracts. Instructs the Under Secretary to ensure that funding and resources expended in international cooperative activities will be equitably matched by the foreign partner organization through direct funding or funding of complimentary activities, or through the provision of staff, facilities, materials, or equipment.

Permits the Under Secretary to make or accept loans of equipment for research and development and comparative testing purposes.

Authorizes the Under Secretary to conduct international cooperative activities jointly with other agencies.

Specifies that foreign partners may include: (1) Israel; (2) the United Kingdom; (3) Canada; (4) Australia; (5) Singapore; and (6) other allies in the global war on terrorism, as appropriate.

Authorizes the Under Secretary, in coordination with the Chief Medical Officer, as part of the international cooperative activities authorized by this Act, to facilitate the development of information sharing and other types of cooperative mechanisms with foreign countries, including African nations, to strengthen American preparedness against threats to the U.S's agricultural and public health sectors from exotic diseases.

Authorizes appropriations to the Secretary of DHS, which shall be derived from amounts otherwise authorized for the Directorate of Science and Technology, for FY2008-FY2011 for activities under this Act.

States that, whenever the Office participates in an international cooperative activity with a foreign country on a cost-sharing basis, any reimbursements or contributions received from that foreign country to meet its share of the project may be credited to appropriate current appropriations accounts of the Directorate of Science and Technology.

Requires the Under Secretary, acting through the Director, to transmit: (1) a specified report to Congress on such international cooperative activities; and (2) updates of such report every five years.
Output: To provide for the establishment of the Science and Technology Homeland Security International Cooperative Programs Office, and for other purposes.