The Yellow Submarine have purchased the 36-year-old striker in the hope that he can help get them back to La Liga following last season's relegation
The veteran striker will be presented to the fans on Tuesday during an open event at the Entrelineas Restaurant, which is attached to El Madrigal, the club's stadium.
The Uruguayan will add depth to a side that hope to get back into La Liga after being relegated last season.
'El Rifle' will join fellow South American and new signing Fernando Cavenaghi in attack while Giuseppe Rossi recovers from a knee injury.
Pandiani spent last season at Espanyol, and has also featured for the likes of Osasuna, Deportivo La Coruna and Mallorca.