Youth Justice Act of 2015

include as one of the purposes of such Act the support of a trauma-informed continuum of programs (including delinquency prevention, intervention, mental health, behavioral health, substance abuse treatment, and aftercare) to address the needs of at-risk youth and youth who come into contact with the justice system;

require the Office of Juvenile Justice and Delinquency Prevention (Office) to develop a long-term plan to improve the juvenile justice system, taking into account scientific knowledge regarding adolescent development and behavior;

include the Administrator of the Substance Abuse and Mental Health Services Administration, the Secretary of Defense, and the Secretary of Agriculture on the Coordinating Council on Juvenile Justice and Delinquency Prevention;

expand the annual reporting requirement of the Office to include information on the use of restraints and isolation upon juveniles held in custody;

require states to implement plans to ensure fairness and reduce racial and ethnic disparities in the detention of juveniles;

enhance requirements for separating juveniles from sight or sound contact with adult lock-ups;

terminate, three years after the enactment of this Act, the authority of a court to issue an order detaining juveniles in adult lockups who have not been charged with adult criminal offenses (status offenders);

require the Office to report annually on policies and procedures to eliminate dangerous practices and unreasonable use of restraints in the detention of juveniles;

expand requirements for state plans for juvenile justice and delinquency prevention to include community-based alternatives to the detention of juveniles in correctional facilities;

provide technical assistance to states and local governments for achieving compliance with the requirements of this Act; and

authorize the Office to make incentive grants to states and local governments to increase the use of evidence-based or promising prevention and intervention programs for juveniles who enter the criminal justice system and for the recruitment and training of professional personnel.

Amends the Incentive Grants for Local Delinquency Prevention Programs Act of 2002 to include mentoring programs in delinquency prevention grant programs.

Requires the Government Accountability Office to conduct: (1) a comprehensive evaluation of the performance of the Office of Juvenile Justice and Delinquency Prevention; and (2) a comprehensive audit and evaluation of selected grant recipients, including a review of internal controls to prevent fraud, waste, and abuse.

Requires audits of all JJDPA grants awarded by the Department of Justice (DOJ). Prohibits: (1) the award of a JJDPA grant to a tax-exempt nonprofit organization that holds money in offshore accounts for the purpose of avoiding the tax on unrelated business income; (2) the hosting or supporting of DOJ conferences that use more than $20,000 of DOJ funds without prior written authorization; and (3) lobbying of representatives of DOJ or of a federal, state, local, or tribal government regarding the award of grant funding.

Amends the Omnibus Crime Control and Safe Streets Act of 1968 to require states, as a condition of receiving juvenile accountability block grants, to provide assurances of compliance with the core requirement of JJDPA applicable to the detention and confinement of juveniles.