2010-11: Ben Harpur played forward and defense for the Niagara Falls Canucks midget AAA team. He had 18 points with 111 penalty minutes in 43 games. Harpur participated in the OMHA Under-17 Program of Excellence Camp in Guelph in May and was selected by Guelph in the third round (43rd overall) of the 2011 OHL Priority Draft.
2011-12: Harpur made his OHL debut as a 16-year-old and skated in 34 games for Guelph in his first season. He had a three point game (1 goal, 2 assists) in a 10-2 win over Erie in his second game but had just 1 assist the rest of the year while seeing limited time. He finished the year +1 with 22 penalty minutes. The Storm finished fourth in the Midwest Division but Harpur did not see any action in the six-game playoff series with Plymouth.
2012-13: Harpur skated in 67 of 68 games for Guelph in his second season. He scored 3 goals with 12 assists and was +14 with 59 penalty minutes. Guelph was once again fourth in the Midwest Division despite finishing with 16 more points than in 2011-12. Harpur had no points and was -2 with 2 penalty minutes in the five-game playoff series with Kitchener. He was ranked 101st amongst North American skaters in Central Scouting's final rankings and was select by Ottawa in the fourth round (108th overall) of the 2013 NHL Draft.