The World Cup winner was back in the squad for Sunday's La Liga contest with Atletico Madrid, having been left out of the previous two matches amid the uncertainty surrounding his future.
Barcelona attempted to sell Dembele in January, with the attacker refusing to sign a new deal, but he will remain at the club until at least the end of the season, when his contract is due to expire.
The 24-year-old was an unused substitute in Barcelona's 4-2 win over Atletico, but a section of the supporters were clearly whistling him during the contest.
Xavi has asked the fans to back all of the players at the club, including Dembele, who is expected to depart on a free transfer at the end of June.
"I would like to ask the fans to please stop whistling at Dembele. He is one more in the group - they did it today, now please stop. We need to support our team, our players," Xavi told reporters.
The win over Atletico has seen Barcelona, who have had a tough campaign to date, move into fourth position in La Liga, but they are still 12 points behind division leaders Real Madrid. body check tags ::