It is represented by several partial skeletons from a single locality within the Coniacian (lower Upper Cretaceous) Sierra Barrosa Formation in the south of Mendoza Province, northern Neuquén Basin, Argentina.

The type species, Mendozasaurus neguyelap, was described by Argentine paleontologist Bernardo Javier González Riga in 2003.

This species belonged to the discovered clade Lognkosauria,[1] a transitional group of titanosaurs which included the gigantic Futalognkosaurus and Puertasaurus.

[2] In 2010 Gregory S. Paul estimated Mendozasaurus at 20 meters (65.6 feet) in length and 16 tonnes (17.6 short tons) in weight.

[3] A phylogenetic analysis conducted by González Riga and colleagues in 2018 recovered Mendozasaurus as the most basal member of Lognkosauria, including Futalognkosaurus and the gigantic titanosaurs Argentinosaurus, Notocolossus, Patagotitan and Puertasaurus.