The ruling was made on Tuesday after a hearing held on September 13 at the Lausanne-based court, reports Efe news.
"The Sole Arbitrator partially upheld the appeal and reduced the suspension imposed by UEFA on Neymar Jr. to two UEFA competition matches for which he would otherwise be eligible," the CAS said in a statement.
The UEFA Control, Ethics and Disciplinary Body opened an inquiry into the Brazilian on March 22 over remarks he made on social media following Paris Saint Germain's 3-1 home defeat to Manchester United in the second leg of a round-of-16 tie, which eliminated the French club from the competition.
United's victory at Parc des Princes was the result of a controversial penalty decision. Going into stoppage time, United led 2-1 on the night, but PSG was still up 3-2 overall.
As the match entered the 95th minute, a shot by United's Diego Dalot bounced off the arm of defender Presnel Kimpembe out of play for a corner. After reviewing the play with the VAR (video assistant referee), the official cited Kimpembe for a handball and awarded a penalty.
Marcus Rashford stepped up to the penalty spot and converted to level the aggregate score at 3-3 and give United the edge on away goals. UEFA penalized Neymar for a social media post following the contest.
"That is a disgrace! And UEFA still pick four guys who know nothing about football to review the VAR decision in slow motion... that handball simply doesn't exist!" he wrote.
Neymar resorted to the CAS after the UEFA appeal committee turned down an appeal filed by the French side on June 18.
( With inputs from IANS )