Gamma-aminobutyric acid (GABA) modulates plant physiological responses under both optimal and stress conditions. Applying GABA externally has shown great potential in improving plant resistance to a range of abiotic stresses. GABA administration stimulates key processes of plant physiology such as nitrogen metabolism, amino acid synthesis, water relations, stomatal conductance, photosynthesis, and chlorophyll metabolism. GABA supports stress adaptation by influencing the expression of genes that regulate nutrient uptake, enhancing the activity of key metabolic enzymes, stabilizing cellular structures, and regulating hormone signalling pathways. It also promotes osmotic adjustment, maintains ion homeostasis, and protects the photosynthetic apparatus under adverse environmental conditions. GABA administration also activates antioxidant defence mechanisms, reduces oxidative stress, and supports cellular energy balance through the GABA shunt. The synergy among diverse physiological responses due to GABA application facilitates stress resilience and prompts growth/productivity augmentation. The mechanisms underlying GABA-mediated stress mitigation offer their potential applications in sustainable agriculture and the improvement of crop performance under challenging environmental conditions.