Hickey was selected by the Los Angeles Kings with the No. 4 pick of the 2007 NHL Draft. He was named a Second Team All-Star in the Western Hockey League for the 2006-07 season after scoring 50 points in 68 games for Seattle.
Hickey returned to Seattle for two more seasons after being drafted, and his offensive game continued to improve. He was a WHL First-Team All-Star in 2007-08 after he scored 11 goals and 45 points and was plus-20. He was team captain in 2008-09, his final season in junior, and again earned WHL First-Team All-Star honors by scoring 16 goals and 51 points and was plus-37.