Cardiff Metropolitan graduate Pearson joined Irish’s senior academy in the summer and has impressed enough to earn a debut.
He is one of three changes to the XV that started in the gripping draw with Gloucester.
Props Will Goodrick-Clarke and Ollie Hoskins have both come into the side, with Allan Dell and Marcel van der Merwe dropping to the bench.
London Irish are still looking for their first win of the season after five games, but Isaac Curtis-Harris believes it will come soon.
“You can see it in training, the messages after the game, the way we speak to each other, we want that first win. We are confident as a group,” he said.
“We keep getting so close to winning, we are literally an inch or two from getting our first win. It didn’t work against Gloucester, but we are chomping at the bit to get another opportunity.”