The TV personality cheered on his team London Wasps as they took on Bath.
The Wasps lost 27-23, but Cipriani said he was glad to be back after an injury.
"I was just happy to get through the match... I felt a bit rusty at first. Now I just want a run of games. I didn't feel any reaction [to the injury]," he told the Daily Mail.
Brook, 28, was first rumoured to be dating the 20-year-old after splitting from actor Billy Zane in August.