A simple spectrophotometric method with good selectivity and high sensitivity towards sulfide ions has been introduced. The method is based on the replacement of the axial water molecule of the aquacyanocobyrinic acid heptamethyl ester (ACCbs) reagent after the reaction with HS- ions, and forming stable complex. ACCbs reagent is characterized with three distinguishable absorption bands with absorption maxima at 353, 497 and 527 nm. After adding HS-, a new absorption band at 582 nm has been obtained. The decrease of the absorption bands of the reaction product at 353, 497 and 527 nm and the enhancement of the band at 582 nm are quantitatively linear to HS- concentration over the concentration range 0.02-1.543 μg mL-1 with lower limit of detection 0.019 μg mL-1. No noticeable interferences are caused by most common ions. Suitability for the assessment of HS- in complex matrices without prior treatment was shown after validation of the method according to the standards of quality assurance. The results compare fairly well with data obtained using the standard method.