A specific GC-MS method has been developed, optimized and validated for the determination of five genotoxic impurities namely Methyl bromide (Me.-Br), Ethyl bromide (Et.-Br), Isopropyl bromide (Ipr.-Br), n-Propyl bromide (n-Pr.-Br) and n-Butyl bromide (n-But.-Br) in Divalproex sodium (DPS) drug substance. Chromatographic separation of five genotoxic impurities was achieved on DB-1 column (30 m × 0.32 mm, 3.0 μm), consists of 100% dimethyl polysiloxane as stationary phase and passing helium carrier gas. The mass fragments (m/z) were selected for the quantification of Me.-Br (m/z 94), Et.-Br (m/z 108), Ipr.-Br (m/z 122), n-Pr.-Br (m/z 122) and n-But.-Br (m/z 136). Bromide ion (m/z 79) was the qualifier ion for the analytes [(Me.-Br), (Et.-Br), (Ipr.-Br), (n-Pr.-Br) and (n-But.-Br)]. The performance of the method was assessed by evaluating the specificity, linearity, sensitivity, precision and accuracy experiments. The established limit of detection and limit of quantification values for the genotoxic impurities were in the range of 0.005-0.019 μg mL-1. The correlation coefficient values of the linearity experiment were in the range of 0.9947-0.9983. The average recoveries for the accuracy were in the range of 97.6-111.3%. The results proved that the method is suitable for the determination of Me.-Br, Et.-Br, Ipr.-Br, n-Pr.-Br and n-But.-Br contents in divalproex sodium.