Neymar, 26, made a shock switch from Barca to Paris Saint-Germain in a world-record €222million move last year.
Iniesta, who will leave Barca at the end of the season after 16 trophy-laden campaigns at his boyhood club, said it would be unusual if Neymar returned to the Camp Nou.
"I don't think there'd be any problems within the dressing room but for me, it would be a bit weird to see him back at Barca," he said on Thursday.
While Iniesta is leaving, Barca are reportedly set to sign Atletico Madrid star Antoine Griezmann in the off-season.
The Spain international said the arrival of Griezmann, 27, would be a huge boost to Barca, though he pointed out that he does not know if the France international will join.
"I know that Griezmann's one of the best strikers around at the moment but I've no idea as to what will happen in the future," Iniesta said.
"As it stands, he is an Atletico player and anything I say about him isn't going to change that.
"If he does end up joining Barcelona, he would be a great signing."