This article reports one-pot synthesis of ten novel spirooxindoles using 5-methyl-2-thiohydantoin, isatin derivatives, and malononitrile in good to high yields (65-90 %). The structures of the synthesized compounds were deduced by ¹H-NMR, ¹³C NMR, FT-IR, and Mass spectral data. The antibacterial activity of the compounds was evaluated against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) based on the Kirby-Bauer method. According to the obtained data, the synthesized compounds show more activity against Gram-positive bacteria than Gram-negative bacteria. Also, the antioxidant activity of these compounds was measured using the DPPH radical scavenging test method, which showed good to excellent activity (59.65–94.03 %). Among them, the chlorinated derivatives (4 f–j) exhibited more antioxidant activity (84.85–94.03 %) than the other compounds (4 a–e) (56.65–74.4 %) and even ascorbic acid as a standard antioxidant compound (82.3 %).