The Chile international defender had been in negotiations for several weeks, but there were delays in completing the move.
According to La Gazzetta dello Sport, Cardiff City faxed the signed and counter-signed documents over on Saturday afternoon.
The deal was confirmed later on Saturday and he should have his first training session at the Pinetina ground tomorrow or Monday.
The rest of the team and coach Walter Mazzarri won’t be there this weekend, as Inter have a friendly away to Eintracht Frankfurt on Sunday.
There was a further clue Medel’s time at Cardiff is over, as the official club website had Kagisho Dikgacoi wearing his number 8 jersey.
- Sports & Recreation
- Cardiff City
- La Gazzetta dello Sport
- Eintracht Frankfurt