Diego Simeoneâs side recorded a 2-1 win over Real Valladolid on the final day of the season to finish two points above rivals Real Madrid.
Atletico fell behind in the first half but fought their way back to secure victory, thanks to goals from Angel Correa and Luis Suarez.
While the Spanish side is still basking in this great victory, Partey can share in their joy as he will also officially be recognised as a champion.
The 27-year-old played three matches for Atletico Madrid before moving to Arsenal last summer, which entitles him to share in their La Liga victory.
According to Spanish football expert Guillem Balague, the midfielder will be officially recognised as a champion, although he wonât get a medal because La Liga doesnât offer medals.
âYes, Thomas Partey is officially LaLiga champion. He played three games [for AtlĂ©tico this season] â two [games] from the start. We donât give medals [in LaLiga] but he is officially champion,â he told Joy Sports.
Partey joined Mikel Artetaâs side from Atletico Madrid on transfer deadline day last summer in a deal worth ÂŁ45 million.
The move saw him overtake Michael Essien as the most expensive Ghanaian footballer of all time.