2010-11: J.J. Piccinich scored 22 goals with 23 assists as a freshman at Paramus High School in New Jersey.
2011-12: Piccinich skated for the North Jersey Avalanche junior team in the Atlantic Youth Hockey league and was the leading scorer for Paramus as a sophomore. He scored 23 goals with 19 assists and had 16 penalty minutes in 22 games for the Avalanche. Piccinich scored 37 goals with 28 assists as Paramus captured the Big North Silver regular season and playoff championships. He was invited to the USA Hockey National Team Development Camp and was selected by London in the sixth round (118th overall) in the 2012 OHL Priority Draft. In June he participated in the Liberty Bell Games tournament for top prospects in the USA Hockey Atlantic District.
2012-13: Piccinich skated in the USHL with the Youngstown Phantoms and in September committed to playing college hockey at Boston University in 2014-15. He scored 3 goals with 12 assists and was -14 with 4 penalty minutes in 63 regular season games. Youngstown finished third in the Eastern Conference and reached the second round in the playoffs. Piccinich scored 1 goal with 1 assist and was +2 in nine playoff games.
2013-14: Piccinich was the second-leading scorer for Youngstown skating on the team’s top line with 2015 draft-eligible Kyle Connor and Maxim Letunov (STL) in what was an otherwise disappointing season for the Phantoms. Piccinich scored 27 goals with 31 assists and was minus-12 with 31 penalty minutes in 60 games; scoring 13 of his goals with 11 assists on the Youngstown power play. The Phantoms missed the playoffs after finishing last in the Eastern Conference. Piccinich was ranked 135th amongst North American skaters in the Central Scouting final rankings and was selected by Toronto in the fourth round (103rd overall) in the 2014 NHL Draft.