2009-10: Shea Theodore played in the Aldergrove MHA and was drafted in the third round (64ht overall) of the 2010 WHL Bantam Draft.
2010-11: Theodore appeared in four WHL games with Seattle, spending the bulk of the season with the Fraser Valley Bruins in the British Columbia midget major league, and played for gold medal-winning Team British Columbia in the 2011 Canada Winter Games. He was scoreless and minus-two with 2 penalty minutes in limited ice time with the Thunderbirds. In 35 games for Fraser Valley he scored 5 goals with 24 assists and had 28 penalty minutes. Fraser Valley finished ninth in the 12-team league. In six games at the CWG he had no points and 24 penalty minutes.
2011-12: Theodore was the top-scoring defenseman for Seattle as a 16-year-old in his first WHL season; playing on a Thunderbirds team that missed the playoffs after finishing last in the U.S. DIvision. He scored 4 goals and led all Seattle skaters with 31 assists in 69 games and was minus-36 with 30 penalty minutes.
2012-13: Theodore was among the leading scorers amongst WHL defensemen, finishing with 19 goals and 31 assists in 71 games, and skated for Canada's gold medal squad at the 2013 U18 World Junior Championship. His minus-24 plus/minus in 71 games for Seattle was an improvement over his rookie season and the Thunderbirds slipped into a playoff spot; finishing one point ahead of last-place Everett in the U.S. Division. In an epic first round series with Kelowna in which five of the seven games went to overtime, Theodore had 2 assists and was plus-one with 4 penalty minutes. He had 5 assists and was plus-five in seven games for Team Canada in Sochi. Theodore was ranked 11th amongst North American skaters in Central Scouting's final rankings prior to the 2013 NHL Draft.
Good puck skills. Efficient power play quarterback. Moves well in all directions. Needs to add weight/muscle.