Freuler made his professional debut with Winterthur at the age of 18 in 2010, making two substitute appearances at the end of the 2009–10 Swiss Challenge League.

[3] Freuler joined a Winterthur side in tenth place in the Challenge League after the first half of the season, just two points above the relegation zone.

Freuler made 29 starts in the 2016–17 season, in which Atalanta finished fourth in the table, a nine place improvement under first-year manager Gian Piero Gasperini.

On 28 April, Freuler scored a late equaliser at home to eventual champions Juventus, derailing their chance to clinch the Scudetto that weekend.

[5] Freuler made his first Europa League group stage appearance against English side Everton, playing the full 90 minutes in a 3–0 victory over the Toffees.

[6] On 14 August 2022, Freuler joined newly-promoted Premier League club Nottingham Forest, leaving Atalanta after six and a half seasons.

[10] He was included in Switzerland's 23-man squad for the 2018 FIFA World Cup in Russia,[11] where he was an unused substitute in all four matches as the Swiss reached the round of 16.

On 2 July 2021, in the quarter-final against Spain, he contributed the assist for Xherdan Shaqiri's equalizing goal, but was later sent off in the 77th minute following a decision many pundits thought was too harsh.

[21] In the round 16 match against Italy, he scored his first goal in the European competition in a 2–0 victory, contributing to his country's first win over their opponent since 1993.