National Guard Investigations Transparency and Improvement Act of 2014 - Codifies the establishment of the Office of Complex Administrative Investigations (the Office) in the Office of the Chief of the National Guard Bureau. Requires the Office to undertake complex administrative investigations of matters relating to members of the National Guard when in state status, including investigations of sexual assault, upon the request of: (1) the Chief; (2) an adjutant general of a state, a territory, or the District of Columbia; (3) a governor of a state or territory; or (4) the Commanding General of the National Guard of the District of Columbia.

Defines "complex administrative investigation" as any investigation specified by the Chief involving factors giving rise to unusual complexity, including: (1) questions of jurisdiction between the United States and a state or territory, (2) matters requiring specialized training among investigating officers, or (3) matters raising the need for an independent investigation to ensure fairness and impartiality.

Requires the Chief to treat any final report of the Office relating to such matters as if it were the report of an inspector general of the Department of Defense (DOD) or a military department.

Directs the Chief to submit to Members of Congress from the state or territory concerned the final report adopted by the Office regarding such an investigation. Requires the Chief to submit to Congress an annual report regarding all investigations undertaken by the Office during the preceding year.