Suarez was appealing his suspension from all football activity, a sanction imposed by FIFA after the striker bit Italy's Giorgio Chiellini during Uruguay's 1-0 World Cup victory on June 24.
He will be allowed to train with his new teammates at the Camp Nou for the duration of the ban, is eligible to return to action on October 25 and will now also be available for Uruguay's upcoming friendlies against Japan and South Korea in September and Saudi Arabia the following month.
"The sanctions imposed on the player by FIFA have been generally confirmed. However, the four-month suspension will apply to official matches only and no longer to other football-related activities (such as training, promotional activities and administrative matters)," read an official statement from CAS.
"The CAS panel found that the sanctions imposed on the player were generally proportionate to the offense committed. It has however considered that the stadium ban and the ban from "any football-related activity" were excessive given that such measures are not appropriate to sanction the offense committed by the player and would still have an impact on his activity after the end of the suspension."
Suarez will miss Barcelona's first eight league matches of the new La Liga season, plus their first three group games in the Champions League. He could make his La Liga debut against Real Madrid on Sunday, October 26.
Suarez made a high-profile $128 million move from Liverpool to Barcelona after he received his original suspension from FIFA. He was also given a nine-match international ban and a fine of 66 million pounds. Both of those sanctions still stand.