Accumulated data from clinical and preclinical studies suggest that, in drug addiction and states of overeating, such as obesity and binge eating disorder (BED), there is an imbalance in circuits that are critical for motivation, reward saliency, executive function, and self-control. Central to these pathologies and the extensive topic of this Review are the aberrations in dopamine (DA) and glutamate (Glu) within the mesolimbic pathway. Group I metabotropic glutamate receptors (mGlus) are highly expressed in the mesolimbic pathway and are poised in key positions to modulate disruptions in synaptic plasticity and neurotransmitter release observed in drug addiction, obesity, and BED. The use of allosteric modulators of group I mGlus has been studied in drug addiction, as they offer several advantages over traditional orthosteric agents. However, they have yet to be studied in obesity or BED. With the substantial overlap between the neurocircuitry involved in drug addiction and eating disorders, group I mGlus may also provide novel targets for obesity and BED.