[1] The club grew thanks to contributions from locals, and played their first competitive league fixture in 1914, again a 3–2 victory, against FC Monthey.

In 1919, Sion formally organised its managerial structure, with Gilliard becoming vice-president and Charles Aymon taking the presidency.

Sion returned to the National League A at the first attempt and secured a second victory in the Swiss Cup, winning 3–2 against Neuchâtel Xamax in 1974.

More success in the Swiss Cup followed, winning the tournament in three consecutive years from 1995 with victories over Grasshopper, Servette and Luzern.

Despite returning to the top division the following season, financial problems plagued the team, culminating in relegation in 2001, the departure of Kadji and a denial of a professional license in 2003.

[7] However, the lengthy legal battle (including the temporary reprieve) meant the ban was only practically instituted beginning in the winter transfer window of the 2010–11 season.

[10] On 30 September 2011, the SFL decided to provisionally qualify the six new signings, namely Stefan Glarner, Billy Ketkeophomphone, Mario Mutsch, Pascal Feindouno, José Gonçalves and Gabri, to comply with the ongoing legal process.

[22] In late December 2011, the Swiss Football Association complied with FIFA's demands and penalized Sion 36 standings points (based on how many matches ineligible players were involved), moving the club to last place in the league standings and putting the club at risk of relegation if the ruling stood.

[23] Sion finished the 2011–12 season in ninth place, which qualified them to the relegation matches against Aarau, whom they defeated 2–1 on aggregate to stay in the Swiss Super League.

Prior to the start of the 2012–13 season, they made a major coup by signing Gennaro Gattuso and Kyle Lafferty, both via free transfers.

In 2022–23, Sion relegation to Challenge League after defeat from Stade Lausanne Ouchy 2-6 and ended top tier in 17 years.

Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply.