Costello was born in
Rutland, Vermont, the son of Bartley Costello, a lawyer, and Catherine (
née O'Brien). He is of Irish descent. He attended
College of the Holy Cross and was commissioned an
ensign through the
NROTC Program in 1973. Costello, by then a vice admiral, reported as commander of the Third Fleet in May 2005 following a tour as chief of legislative affairs. His sea tours include: navigator in
Brownson; weapons officer in
Whipple; operations officer of Destroyer Squadron Five; executive officer in
Harry W. Hill; commanding officer in
Elliot; assistant chief of staff for operations, Third Fleet; commander,
Destroyer Squadron 23;
commander, Cruiser Destroyer Group One, Constellation Strike Group commander, and commander of Task Force 55 during
Operation Iraqi Freedom. He attended
Albany Law School, where he earned a
Juris Doctor degree and is currently a member of the New York State Bar. He also attended the
College of Naval Command and Staff, where he was selected as honor graduate, graduating "With Distinction," and earned a Master of Arts degree in foreign affairs. Additionally, he has participated in the National Security program at
John F. Kennedy School of Government at
Harvard University. Costello's primary shore assignments include: joint planner in the Operational and Interoperability Directorate (J7), the Joint Staff, and principal deputy for senate liaison in the navy's
Office of Legislative Affairs; and deputy director for strategy and policy (J5), the
Joint Staff. ==Awards and decorations==