To reduce cadmium (Cd) accumulation in rice, the effects of gamma-aminobutyric acid (GABA) on growth and Cd accumulation in rice seedlings were investigated in a pot experiment under Cd stress. The results indicated that treatment with 1 mg/L Cd significantly decreased the biomass, photosynthetic pigment content, photosynthesis rate, and antioxidant enzyme activity of rice seedlings. Consequently, exposure to 1 mg/L Cd-induced stress in rice seedlings, thereby inhibiting the growth of rice seedlings. Under Cd stress, concentrations of 0.1, 0.25, and 0.5 mmol/L GABA enhanced the biomass, photosynthetic pigment content, and photosynthesis of rice seedlings, whereas a concentration of 1 mmol/L GABA did not significantly affect these parameters. Lower concentrations (0.1 and 0.25 mmol/L) of GABA reduced the antioxidant enzyme activity and Cd contents in the roots, stems, and sheaths of rice seedlings under Cd stress, whereas higher concentrations (0.5 and 1 mmol/L) increased these parameters. Specifically, the concentrations of 0.1, 0.25, 0.5, and 1 mmol/L GABA decreased leaf Cd content by 78.79%, 71.74%, 56.77%, and 28.82%, respectively, compared with the Cd treatment. Therefore, the concentrations of 0.1 and 0.25 mmol/L GABA not only promote the growth of rice but also reduce Cd accumulation in rice under Cd stress.