G protein-coupled receptors (GPCRs) are central regulators of neurotransmission and neuroplasticity, influencing the pharmacodynamics of psychoactive substances. As key nodes in signal transduction, they modulate second messenger systems, ion channel activity, and synaptic communication. Despite extensive research on GPCRs as therapeutic targets, their specific role in addiction-related neuroadaptations remains insufficiently understood. This review systematically examines how core GPCR subtypes; dopamine, opioid, cannabinoid, and metabotropic glutamate receptors mediate the reinforcing properties of addictive drugs. It highlights the dual roles of GPCR-dependent and independent pathways in altering reward circuitry and driving compulsive drug-seeking. The review also explores recent innovations in structure-based drug design, including biased agonism, allosteric modulators, and GPCR conformational dynamics, for next-generation addiction therapies. By integrating molecular pharmacology with addiction neuroscience, this review identifies translational challenges and opportunities, underscoring the value of GPCR-targeted pharmacotherapies. Ultimately, it advocates for interdisciplinary strategies to bridge preclinical findings with effective clinical interventions for substance use disorders.