Strengthening Domestic Nuclear Security Act of 2014

Strengthening Domestic Nuclear Security Act of 2014 - Amends the Homeland Security Act of 2002 to authorize appropriations for the Domestic Nuclear Detection Office for FY2015-FY2016.

Requires the Director for Domestic Nuclear Detection: (1) in developing and implementing the enhanced global nuclear detection architecture, to provide support for planning, organization, equipment, training, exercises, and operational assessments to federal, state, local, territorial, and tribal entities to assist in implementing radiological and nuclear detection capabilities in the event of a radiological or nuclear act of terror or other attack; and (2) to establish the Securing the Cities (STC) program to enhance the ability of the United States to detect and prevent a radiological or nuclear act of terror or other attack in high-risk urban areas. Requires the Comptroller General (GAO) to submit to specified congressional committees an assessment of the STC program within one year after enactment of this Act.

Requires, in the event of an acquisition of a new system for a component of DHS or any other DHS-related or -associated end-user, the head of such component to complete and sign a Mission Need Statement and Operational Requirements Document.

Amends the Homeland Security Act of 2002 to change the joint annual interagency review of global nuclear detection architecture and the required annual report thereon to a biennial review and report.