Cavallini began playing for Nacional's youth development squads in 2010. In June 2011, he participated in the 2011 U-20 Copa Libertadores. In the first game, Nacional beat Libertad 1–0 with a goal by Romero. In the second match, they beat Jorge Wilstermann 3–1 with goals from Bueno, Marchelli and again Romero. In the third and final game, Nacional drew 0–0 with Universitario, and qualified for the quarterfinals. On June 20, they were defeated by Mexican side América 1–0, which led to their elimination. His development in the youth squad lead him to sign a senior contract with the club in early 2012.
Juventud
In mid July 2012, he was sent on loan to Juventud de Las Piedras in order to make his professional debut and have more chances in the first team. In his second match with the club, he scored his first official goal in the 1–0 home victory against Central Español. On October 7, he was the man of the match against Bella Vista, assisting and scoring a goal in his team's 2–0 victory. His third goal came six days later, in a 1–1 away draw against Fénix.
Cavallini was loaned to Liga MX side Puebla on August 31, 2017, becoming the first Canadian to play in Mexico's top tier since Isidro Sánchez Macip in 2010. He would debut for the club against Cruz Azul on September 9, coming on in the 64th minute for Félix Micolta in a 0–0 draw. He scored his first goal for Puebla against Necaxa on September 16. After scoring 13 goals in 25 matches for Puebla in the 2017-18 season, the club would sign him to a four-year contract in June 2018.
Vancouver Whitecaps FC
Puebla and Cavallini agreed to a transfer, signing a three-year deal with MLS side Vancouver Whitecaps FC for a club-record transfer fee ahead of their 2020 season on a three-year deal.
International career
Cavallini launched his international career for Canada at 18 years old, debuting for the U-20 team in 2011 during the CONCACAF U-20 Championship in Guatemala. Cavallini has earned three call-ups to Canada's U-23 National team and his performance, along with the fact that he "plays in a different type of league ", according to head coachStephen Hart, earned him his first call up to the senior roster to face Trinidad & Tobago in a friendly match on August 13, 2012. Cavallini made his debut for Canada as a second-half substitute for Terry Dunfield against Trinidad, a 2–0 victory. Cavallini made his World Cup qualifying debut in Canada's 8–1 loss to Honduras. Following that match, he declined a call-up from interim coach Colin Miller for the 2013 Gold Cup, citing personal reasons. Then coach Benito Floro gave an interview in October 2014 where he elaborated on Cavallini, saying that he had reached out to the player and had not heard back from him. Floro however pointed out that there is a place in the team for him in the future. In May 2015, Cavallini stated in an interview with Tenfield that he regretted becoming cap-tied to Canada. Despite his comments, Cavallini was called up to face Ghana in an October 2015 friendly. In an interview regarding his return to the national team, Cavallini stated that he never said he wouldn't play for Les Rouges again, and that his comments were wrongly translated. He mentioned that his lack of appearances were related to personal matters and timing including the birth of his daughter. Cavallini was named to the Canadian 40-man provisional team for the 2017 CONCACAF Gold Cup by Canada coach Octavio Zambrano on June 6, 2017. He was confirmed as part of the final 23-man squad on June 27. Cavallini scored his first goals for Canada on September 9, 2018, netting a brace in an 8–0 victory over the U.S. Virgin Islands in a CONCACAF Nations League qualifier. On May 30, 2019, Cavallini was named to the final squad for the 2019 CONCACAF Gold Cup. He scored a hat-trick in a 7–0 win over Cuba during the group stage on June 23, and had a chance to score his fourth goal from a penalty spot, but his panenka went over the crossbar.
