The 20-year-old had a spell on trial with the Bluebirds, who confirmed the signing on their club website, earlier this summer and he impressed manager Malky Mackay enough to secure a move from CA Progreso on a four-year contract.
The centre-half was part of the Uruguay Under-20's squad that finished runners-up to France in the World Cup in Turkey.
He joins Andreas Cornelius, John Brayford, Simon Moore, Steven Caulker and Gary Medel in joining Cardiff for their maiden Premier League campaign.
A statement on the Cardiff website read: "Cardiff City Football Club is pleased to announce the signing of Uruguayan U20 international, Maximiliano Amondarain."
Source: PA
Source: PA