The former Sweden international represented both clubs during his career and became a favourite with both sets of supporters.
Despite insisting that he will sit on the fence, the 41-year-old believes that Barca are the favourites to take maximum points.
"I remember my time at Celtic and Barcelona fondly," he said. "They are two important clubs that represent two different cities and cultures.
"I can't choose between them because it wouldn't be fair on me, so here's hoping the best team wins and they put on a real show. That said, I think Barca is the favourite."
Larsson scored 242 goals for the Bhoys and found the net on 19 occasions for Barca.