Energy metabolism in the brain accounts for approximately 20% of the body’s oxygen consumption being glutamatergic transmission a major contributor. To meet these energetic requirements there is a tight coupling between neurons and astrocytes. Thus, neuronal glutamatergic activity decreases astrocytic oxidative glucose metabolism in favor of glucose metabolism to lactate. Lactate released by astrocytes can be oxidatively metabolized by neurons. However, little is known about the interplay between neuronal activity and astrocytic metabolism concerning other energetic sources. Here, we made use of primary cultured rat astrocytes to show that glutamatergic neurotransmission also decreases mitochondrial fatty acid beta-oxidation and oxygen consumption thereby increasing the local oxygen availability. Such effect is independent of brain area and reproduced in human cortical astrocytes. Mechanistically, glutamate inhibition of fatty acid metabolism involves GLAST/EAAT1 transporters but not activation of glutamate metabotropic nor NMDA or AMPA receptors. Glutamate, which alters mitochondrial pH, does not affect Acetyl-CoA Carboxylase phosphorylation status, responsible to produce malonyl-CoA, the endogenous inhibitor of fatty acid oxidation. Importantly, this glutamatergic-induced metabolic adaptation ensures astrocytic survival. In conclusion, glutamatergic regulation of astrocytic use of glucose and fatty acids provides the brain with metabolic flexibility able to perfectly couple and fulfill neuronal activity and astrocytic functions.