Bowen, son of former Scarlets fly-half Gareth, was with Bristol Bears while studying at Clifton College and signed for Cardiff in 2024, making his senior debut against Cheetahs in December of that year.
The 5ft 7in (1.73m) wing was mentioned as a potential bolter for Steve Tandy’s first Wales squad in the autumn but has been left to develop in club rugby and with the under-20s.
Bowen started all five games of his final U20 Six Nations, scoring a double in Ireland, and is poised to feature at the World Rugby Junior World Championship in Georgia this summer.
“He is a young, exciting player who is a big part of our future,” said Cardiff coach Corniel van Zyl.
“His point of difference is obviously his finishing – he has the ability to finish opportunities that not many other players could.
“He is also a great person, who is eager to learn and improve. The key thing for Tom now, is continuing to develop his all-round game as a wing on the back of some impressive games for us and a really good Six Nations.”