Evans has signed a short-term contract with the Blue and Blacks until the end of the season.
The 27-year-old tight-head specialist returns to his roots, having won Welsh Schools and Under-19 caps while playing for Cardiff Youth.
Now Evans has earned 22 senior Wales caps, and has won both the cup and league with Swansea, but following the All Whites move to temporary administration earlier this season, he has decided his future lies elsewhere.
Ironically, Evans trained with Pontypridd earlier in the week with a view to joining the Principality Cup holders, and will go into Friday's TV showpiece game with some inside knowledge of Mefin Davies' side.
Evans is able to play for Cardiff in the cup quarter-final because he missed the last round match against Caerphilly due to Welsh squad commitments.
If Cardiff win, he could yet go on to meet his former teammates from St Helen's in either the semi-final or final, with Swansea playing Bridgend in the crunch quarter-final.
Cardiff coach Dai Young said: "Ben is a great acquisition for us. He is a proven international and I am delighted to welcome him back to a club he played for as a youth.
"We've always regarded him as a Cardiff man, and initially he's with us until the end of the season, and hopefully beyond that."
Evans played a handful of first-class games for Cardiff before becoming a student at UWIC.
He then joined Neath and moved to Swansea in 1998 shortly after winning his first cap on the summer tour to South Africa.
At 6ft 3in and 18st 10lbs, the giant prop was a mainstay in the Wales team that won 10 successive games under Graham Henry.