2009-10: Tommy Vannelli played in 27 games as a ninth grader at Holy Family Catholic High School in Minnesota. He scored 2 goals with 8 assists and had 16 penalty minutes.
2010-11: Vannelli skated for the junior varsity team at Minnetonka High School after transferring from Holy Family Catholic for his sophomore year.
2011-12: Vannelli was the leading scorer amongst defensemen for Minnetonka as a junior and open the eyes of scouts with his play at the USA Hockey Select 17 Festival in June. He scored 7 goals with 18 assists in 28 games and was plus-21 with 8 penalty minutes. The Skippers finished first in the Lake Conference and reached the Section 6AA championship game against eventual AA state champion Benilde-St. Margaret's. Vannelli was selected by the Tri-City Storm in the 16th round (230th overall) of the 2012 USHL Entry Draft.
2012-13: Vannelli skated for the USA in the 2012 U18 Ivan Hlinka Tournament in August and played for Team Northwest in the Upper Midwest Elite League in the fall before returning to Minnetonka for his senior season. Vannelli was the only player not in National Team Development Program to skate for the USA at the 2013 U18 World Junior Championship. He was the third-leading scorer for the Skippers, scoring 10 goals with 25 assists in 27 games and was plus-23 with 14 penalty minutes. Minnetonka lost in the Section 6AA semifinals. Vannelli skated in 11 USHL games with the NTDP team and was plus-seven with 1 goal and 1 assist and at the WJC tournament in Sochi he scored 2 goals with 1 assist and was an even plus/minus in seven games as USA won a bronze medal. In December he committed to playing college hockey at the University of Minnesota. Vannelli, ranked 77th amongst North American skaters in Central Scouting's mid-term rankings, was ranked 44th in the final rankings prior to the 2013 NHL Draft.
Vannelli has informed the University of Minnesota that he will not play for that school in 2013-14. Instead, he may end up in the WHL with the Medicine Hat Tigers, or he could go the USHL route if he wants to retain NCAA eligibility.