To mitigate the stress of cadmium (Cd) on crops and reduce Cd accumulation in crops, maize (Zea mays) seedlings were treated with gamma-aminobutyric acid (GABA, 0.5 mmol L−1) irrigation under Cd stress conditions. The effects of GABA on the physiology and Cd uptake of maize seedlings were investigated through a pot experiment. Results showed that under Cd stress, applying 0.5 mmol L−1 exogenous GABA decreased maize seedling root and shoot biomass by 5.85% and 3.85%, respectively, compared to Cd treatment alone. Exogenous GABA also reduced the levels of photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoid) in maize seedlings under Cd stress. Regarding antioxidant enzyme activity, exogenous GABA increased the activities of peroxidase (POD) and superoxide dismutase (SOD) in maize seedlings under Cd stress while having no effect on catalase activity. In addition, exogenous GABA irrigation increased the concentrations of root Cd and shoot Cd in maize seedlings by 11.93% and 23.22%, respectively, compared to Cd treatment alone. Therefore, the irrigation of exogenous GABA (0.5 mmol L−1) is found to inhibit growth and promote Cd uptake in maize seedlings under Cd stress conditions.