Four new 2-thiohydantoin derivatives (4a-d) were synthesized from the reaction of maleimide derivatives (3a-d) with phenylisothiocyanate. The structures of synthetic compounds were characterized using Fourier-transform infrared spectroscopy (FT-IR), 1H- and 13C-nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry. The antioxidant activity of the synthesized compounds showed inactive 4b and 4c compounds, moderately active 4a, and strongly active 4d, compared with vitamin C as positive control (IC50 values = 1.380, 1.726, 4.147, 8.085, and 9.826 µM, respectively). Antibacterial and antifungal activities of compounds showed that only compound 4b had an effect on Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger species.