The 26-year-old Medic joins Norwich on a three-year deal, keeping him at Carrow Road until 2028.
Norwich and Ajax have not made the transfer fee public, but Dutch media report that Ajax receive €2.5 million for the flopped centre-half.
"I'm really happy to come here to sign for this club," Medic said on the club website. "An historic club, a club I know that are really good and I'm really happy to be here.
"From the first moment that they contacted me and my agent, we spoke and I was really happy that they wanted me and they've followed me for a long time. For me, it's a really good step. I've always had a wish to play here in England, so I didn't think so much about this decision to become a player at Norwich."
Electric debut
Medic joined Ajax in 2023 from German side St. Pauli, but failed to make an impact past his debut, in which he scored Ajax's goal of the season against Heracles Almelo.
In his one full season with Ajax, Medic played just nine games across all competitions. The Croatian centre-half was sent out on loan to Bundesliga side VfL Bochum for the 2024/25 season, with whom the Croatian centre-half relegated from the Bundesliga.
"There was no real prospect for Jakov at Ajax, so it made sense for both parties to look elsewhere," Ajax technical director Alex Kroes said on the club website.
"At Norwich City, he faces an exciting challenge in the Championship. We have wished him all the best for the next step in his career."
Medic was under contract until 2028 at the Amsterdam side.