Player-of-the-tournament Jonathan Joseph inspired the Exlies to a 31-28 victory in the final of JP Morgan Premiership Sevens.
The young England centre scored two late tries to help overturn a 28-5 deficit as Irish put on a superb second-half comeback against Gloucester.
Speaking after the tournament, Joseph said: "It's overwhelming. We were under it from the beginning. We went down so much, but we dug deep. All the boys worked hard. We knew what was at stake and it came off.
"A lot of people have written us off this year. We had a not so good season last year and people were saying we were not going to do too well and we really wanted to make a statement and prove that we are up there and can challenge for silverware."
The Irish were led by former England Under-20s captain Alex Gray.