The rocker teamed his yellow coat with a black hat and sunglasses, with the whole ensemble contributing to his bizarre appearance.
But his weight gain appears to have continued over the past year and a half, with Rose looking entirely different as he performed in Brazil.
Gearing up for the performance, Rose told eager fans he was concerned that the pouring rain would make the stage treacherous for the concert.
He said: 'Good evening… good morning! Please bear with us and give us a little second here to figure out what to do about not falling on our asses.
I'm going to try to focus on singing rather than running around like an idiot. I'm better at being an idiot. We want everybody to be careful.'
The group then delighted fans with tracks including Sweet Child of Mine, Live and Let Die and Welcome to the Jungle.
The band's performance was their first since last December, and came ahead of the Guns N' Roses' US tour which begins later this month.
The tour will start in Orlando on October 28th and finishes on December 1st in Auburn Hills.