Celtic received new life in Europe as it was reinstated in the Europa League on Friday.
Celtic was eliminated prior to the group stage against Sion, but a complaint was filed by the Scottish club because of the belief the Swiss club fielded ineligible players.
UEFA upheld the club's complaint, finding that Sion fielded ineligible players in the two-legged qualification series. Pascal Feindouno, Gabri, Mario Mutsch, Jose Goncalves and Billy Ketkeophomphone were all ineligible.
"We have been advised by UEFA that the two protests relating to the matches against FC Sion have been upheld, as a result of which each match has been forfeited in favor of Celtic," Celtic posted on its website.
"We are pleased by this decision, the approach which has been taken by UEFA and the fact that UEFA rules and regulations have been upheld. We are also grateful for the support of the SFA in this matter."
Sion won the series after a 0-0 draw in Glasgow and a 3-1 win in Switzerland, but Celtic has now been awarded a pair of 3-0 forfeits.
Celtic will take Sion's place in Group I, and plays Atletico Madrid, Udinese and Rennes in one of the toughest groups in the competition. Celtic will visit to Madrid on Sept. 15 for its first match of the stage.