The former Cameroon international has sealed a move to the Swiss top-flight side in a deal that runs through till the summer of 2020
Alex Song has joined FC Sion in a two-year deal on a free transfer.
The former Arsenal and Barcelona star left Russian side Rubin Kazan in January, but trained with the Swiss top-flight side weeks before a deal was announced on Tuesday.
Song started his professional career with French side Bastia and rose to prominence at Arsenal where he made over 200 appearances before moving to Barcelona.
In Spain, however, he struggled and was temporarily shipped back to England twice with Aston Villa. In 2016, The ex-Cameroon international secured a permanent move to Kazan.
Now, he gets to feature for Maurizio Jacobacci's side for the next two seasons.
The Stade de Tourbillon outfit are fifth in the four-week-old Swiss Super League 2018-19 campaign, having gathered six points from their opening four games.