Leon was called to the Canada U-20 camp in December 2009 and played the 2012 FIFA U-20 Women’s World Cup for Canada. In December 2012, she was called up to the senior Canadian team for the 2013 Four Nations Tournament, making her first international appearance against China on January 12, 2013, scoring the game-winning goal in a 1–0 victory.

Born in Mississauga, Ontario, Leon was raised in Maple and moved with her family to King City in 2010 at the age of 16. Her family is connected to Leon’s Furniture. She grew up playing soccer, hockey and rugby.

Leon accepted an athletic scholarship to attend the University of Notre Dame and played for the Notre Dame Fighting Irish women’s soccer team in 2010 and 2011. As a freshman in 2010, she came off the bench to score the Irish’s lone goal in their 1–0 victory over the Stanford Cardinal in the title game of the NCAA national championship tournament. As a sophomore, she was the second leading scorer for the Irish.

After her sophomore season, Leon transferred to the University of Florida, where she played for coach Becky Burleigh’s Florida Gators women’s soccer team in 2012. She was the Gators’ sixth leading scorer despite missing her first three matches while she was touring Japan with the Canadian national U-20 team. Leon scored four game-winning goals for the Gators and helped lead the team to Southeastern Conference regular season and tournament championships.

In 2013, as part of the NWSL Player Allocation, Leon joined the Boston Breakers in the new National Women’s Soccer League. Leon scored her first goal in a 5–1 loss against Sky Blue FC on June 1, 2013.

On June 29, 2013, the Boston Breakers traded her to the Chicago Red Stars for her Canadian national teammate, Carmelina Moscato.

In November 2015, the Chicago Red Stars traded her to the Western New York Flash. She transferred to FC Zürich Frauen of the Swiss Nationalliga A on August 30, 2016.

FC Zürich Frauen reported on December 1, 2016, that Leon and team management had mutually decided not to renew her contract for the upcoming Nationalliga A season.

On January 30, 2017, it was announced that Leon had signed back on with the Boston Breakers for their 2017 campaign.

On May 2, 2017, Leon was named NWSL player of the week for week 3 for her performance against Seattle Reign. Leon was credited with 2 assists and 1 goal in Boston’s 3–0 victory.

The Breakers ceased operations prior to the 2018 season. Leon was picked up by Sky Blue in the dispersal draft on January 30, 2018. On June 12, 2018, Leon was traded to the Seattle Reign in exchange for a fourth round pick in the 2019 NWSL College Draft. Leon made six appearances for Seattle in 2018.

At the 2018 CONCACAF Women’s Championship Leon scored 6 goals and finished second in tournament’s golden boot race behind Alex Morgan of the United States who scored 7 goals.

On January 3, 2019, the Seattle Reign announced that they had not retained Leon’s NWSL rights for the 2019 season. This allowed the other eight NWSL teams an opportunity to claim her rights during the distribution process, but none did so. Shortly afterwards it was reported that Leon had accepted an offer from Europe, believed to be from English FA WSL club West Ham.

On May 25, 2019 she was named to the roster for the 2019 FIFA Women’s World Cup.