© 2018 Taylor & Francis.In this study, a new approach is proposed for low cost, sensitive, rapid, and selective detection of sulfide based on its electrocatalytic oxidation at a calmagite-modified pencil graphite electrode. The calmagite-modified pencil graphite electrode was prepared through electropolymerization in which five successive cyclic voltammograms of 0.10 mM monomer on a pencil graphite electrode were recorded in pH 2.0 Britton-Robinson buffer containing 0.10M NaNO3. Cyclic voltammograms of the prepared polycalmagite-modified pencil graphite electrode show that the peak potential of sulfide shifted from +420 mV at an unmodified pencil graphite electrode to +250 mV at the proposed electrode. The results show that a polycalmagite-modified pencil graphite electrode exhibits good electrocatalytic response to the oxidation of sulfide. Flow injection analysis of the sulfide at the polycalmagite-modified pencil graphite electrode was performed under optimized conditions using a homemade electrochemical flow cell constructed specially for the pencil graphite electrode. The anodic peak currents obtained from flow injection amperometric curves at +250 mV in pH 9.0 Britton-Robinson buffer containing 1.0M KCl show that the polycalmagite-modified pencil graphite electrode gave a linear range of 0.10-500.0 µM and a detection limit of 0.03 µM. The modified electrode was successfully applied to determine sulfide in real samples, and the method was also verified with recovery studies.