Atletico Madrid have signed Pizzi from Sporting Braga on loan until the end of the year with the option to recruit him on a permanent contract thereafter.
The Spanish club made the announcement on their official website on Monday in which they outlined that the forward will be on loan at the Vicente Calderon until December 31, 2011.
Reports in Portugal suggest that Atletico would have to pay Braga a transfer fee of €15 million (£13.2m) if they would then want to make the deal permanent.
Pizzi, whose full name is Luis Miguel Afonso Fernandes, passed his medical examination with the La Liga outfit on Monday morning and subsequently signed the required documents.
The 21-year-old is a Portugal Under-21 international and is one of a number of signings Atletico have made during the summer transfer window so far, including striker Radamel Falcao from Porto and Arda Turan from Galatasaray.