A novel, simple, sensitive spectrophotometric method is proposed for the determination of cobalt(II). Chloromine-T with iodine in acetic acid produces iodine monochloride, which oxidizes promethazine hydrochloride and diphenylamine to absorbing cations. Those would associate later with cobalt complex to form an ion pair, [Ph+] [CoCl4]- and [Dh2+] [CoCl4]-2 in acid medium. These appear to provide exceptional color stability to the systems. The results compare favorably with those of reported method. The conditions required for the determination of cobalt(II) are described and related analytical parameters are also calculated.