The reaction of N-alkyl 2-nitrobenzenesulfenanilides (1a-3a) with N-bromosuccinimide (NBS) gave the corresponding monobrominated 2-nitrobenzensulfenanilides (1b-3b) in good yields. The initial step of this reaction is the attack on NBS of the nitrogen atom of 1a-3a. The intermediate of this reaction is considered to be a cation radical of the sulfenanilides. A similar reaction of N-unsubstituted 2-nitrobenzenesulfenanilides (5a-10a) with NBS gave mono- or di-brominated 2-nitrobenzenesulfenanilides in low yields.