2010-11: Seamus Malone played in the Chicago Mission program in Illinois and was invited to participate in USA Hockey's 2011 Select 15 Player Development Camp in July.
2011-12: Malone played for the Chicago Mission midwest champion U16 team that competed in USA Hockey's Tier 1 National Tournament. He scored 13 goals with 20 assists and had 65 penalty minutes in 28 regular season games. Malone was invited to USA Hockey's 2012 Select 16 Player Development Camp and was chosen to represent the USA at the U17 Five Nations Cup in the Czech Republic in August. In March he committed to playing college hockey at Wisconsin in 2015-16. Malone was selected by Plymouth in the 14th round (281st overall) of the 2012 OHL Priority Draft.
2012-13: Malone skated for the gold medal-winning USA U17 team at the 2012 Five Nations Tournament in Chomutov before joining the USHL's Dubuque Fighting Saints for his first junior season. Malone scored 6 goals with 21 assists and was +12 with 44 penalty minutes in 50 games for Dubuque. The Fighting Saints finished first in the Eastern Conference and captured the USHL's Clark Cup; sweeping Fargo in the playoff finals. Malone scored 2 goals with 1 assist and was +1 in nine playoff games. He scored 2 goals with 2 assists and had 4 penalty minutes in four games for Team USA.
2013-14: Malone began the season in Russia as Dubuque competed in the 2013 Junior Club World Cup and played for the USA's U19 team in the 2013 World Junior A Challenge. Malone scored 2 goals with 1 assist in four games at the club tournament as Dubuque won a bronze medal. He scored 1 goal with 2 penalty minutes in four games as the USA finished first in the WJAC. Malone played in the 2013 USA Hockey/CCCM All-American Prospects game and was ranked 128th amongst North American skaters in Central Scouting's mid-term rankings prior to the 2014 NHL Draft.