"Amargasaurus" was discovered in sedimentary rocks of the La Amarga Formation, which dates back to the Barremian and late Aptian stages of the Early Cretaceous. A herbivore, it shared its environment with at least three other sauropod genera, which might have exploited different food sources in order to reduce competition. "Amargasaurus" probably fed at mid-height, as shown by the orientation of its inner ear and the articulation of its neck vertebrae, which suggest a habitual position of the snout above the ground and a maximum height of . Within the Sauropoda, "Amargasaurus" is classified as a member of the family Dicraeosauridae, which differs from other sauropods in showing shorter necks and smaller body sizes.