PSG and Neymar had appealed against the three-game ban imposed by European governing body UEFA in June, and CAS partially upheld the appeal.
Neymar labelled the Video Assistant Referee system "a disgrace" after PSG were eliminated from the Champions League round of 16 by Manchester United after the Premier League side were awarded a decisive last-gasp penalty in a 3-1 win at the Parc des Princes.
Although Neymar will still miss Real Madrid at home on Wednesday and Galatasaray away in early October in Group A, he will now be back in time for the trip to face Club Brugge in late October.
The 27-year-old made his PSG return in last weekend's Ligue 1 win over Strasbourg, scoring a late winner after being jeered by his club's ultras.
As well as Neymar, PSG will also be missing Kylian Mbappe and Edinson Cavani against in their Champions League opener against Madrid.
Information from Reuters was used in this report.