The 29-year-old, who made 91 appearances in five seasons with Ospreys, appeared set to put pen-to-paper on a deal worth £400,000-a-year in France only for the move to break down.
That paved the way for the Blues to raid their Pro14 rivals and take Arhip to Arms Park ahead of the 2018-19 season.
Speaking about his first big signing as new Blues head coach John Mulvihill said: "He has proven himself a world-class tight-head prop both in terms of scrummaging and around the pitch and is the perfect fit for us.
"We need to add quality and depth to our squad to compete in both the Guinness Pro14 and the Champions Cup and this is a great start to our recruitment."
Arhip, who will fight it out with Dillon Lewis for the number three jersey at Cardiff, added: "I'm really excited to be joining Cardiff Blues at a really positive time for the region.
"I have been very impressed with the progress made at the Arms Park in the last couple of seasons, culminating in winning the Challenge Cup."