Combating Military Sexual Assault Act of 2013

Combating Military Sexual Assault Act of 2013 - Directs each military department Secretary to implement a program providing a Special Victims' Counsel (Counsel) to a victim of a sexual assault committed by a member of the Armed Forces (member). Outlines Counsel qualifications and duties, including providing legal representation and assistance in connection with criminal and civil legal matters related to the assault. Provides conditions for legal representation in court, and requires the Manual for Courts-Martial to be revised to allow for such representation.

Allows a member or member dependent who is a victim of a sexual assault by another member to receive Counsel assistance. Requires such victim to be informed of the availability of such assistance at the time the victim originally seeks assistance from a sexual response coordinator or sexual assault victim advocate, a military criminal investigator, a victim/witness liaison, a trial counsel, health care providers, or any other personnel designated by the Secretary concerned. Makes such assistance available regardless of whether the victim elects unrestricted or restricted (confidential) reporting of the incident.

Provides additional duties of the Director of the Sexual Assault Prevention and Response Office within the Department of Defense (DOD), including: (1) providing guidance and assistance for the military departments in addressing matters relating to sexual assault prevention and response, (2) acting as liaison between DOD and other federal and state agencies on sexual assault prevention and response programs, and (3) overseeing development of program guidance and joint planning objectives in support of such program. Requires the Director to also collect, maintain, and disseminate data of the military departments concerning sexual assault prevention and response.

Amends the Uniform Code of Military Justice (UCMJ) to provide for disposition and other requirements in connection with sex-related offenses, and to provide for victims' rights under such actions (including the right to a Counsel).

Requires a convening authority (the official acting on the sentence of a court-martial), when taking any action other than approving a sentence, to prepare a written justification of such action which shall be made part of the record of the court-martial. Prohibits a convening authority from: (1) dismissing or setting aside a finding of guilty, or (2) reducing a finding of guilty to a finding of guilty to a lesser included offense.

Amends the National Defense Authorization Act for Fiscal Year 2012 to require the National Guard of each state and territory to ensure that a sexual assault response coordinator is available at all times to its members.