2008-09: Wacey Hamilton missed much of his second season with WHL Medicine Hat due to injury – appearing in just 37 regular season games. He scored 4 goals with 13 assists and was +9 with 9 PMs for the Tigers, who finished second in the Central Division. Hamilton skated in all 11 playoff games for Medicine Hat and was -3 with 1 goal, 3 assists, and 24 PMs.
2009-10: Hamilton was named team captain and was an offensive and physical force in his third WHL season with Medicine Hat. He was the Tigers' second-leading scorer with 24 goals and 47 assists and hit the century mark with 100 PMs. Hamilton had the top plus/minus (+28) on a Medicine Hat team that finished third in the tough Central Division. He skated in all 12 playoff games for the Tigers, scoring 3 goals with 5 assists and was -1 with 20 PMs. Hamilton represented the WHL in the Subway Super Series.
2010-11: Hamilton returned to Medicine Hat for a fourth season of junior hockey as an over-age, 20-year-old. He was once again the Tigers' captain and was the team's third-leading scorer. Hamilton scored 20 goals and was second on the team with 53 assists as Medicine reached the 100-point mark and finished second in a Central division that featured three of the WHL's top teams (WHL playoff champ Kootenay finished third). He was third on the team with 113 PMs and was +16 in 67 regular season games. He skated in all 15 playoff games as the Tigers reached the finals and scored 4 goals with 8 assists and was -1 with 20 PMs. Hamilton was signed as a free agent to a three-year, entry-level contract by the Ottawa Senators in March 2011.
2011-12: Hamilton played 74 games for the Senators AHL affiliate Binghamton in his first pro season. Playing mostly a fourth-line, energy-type role, he scored 5 goals with 6 assists and was minus-18 with 46 penalty minutes. Binghamton missed the AHL playoffs; finishing fifth in the East Division. Hamilton also played two ECHL games with Elmira, finishing plus-one with a pair of assists.