Abstract Methylsiothiazolinone (MIT) is a wide spectrum biocide used in different industrial fields. In this paper, the electrochemical behaviour of MIT on gold electrode has been studied and square wave voltammetric methods have been developed to determine this compound at different concentration levels. MIT exhibited and irreversible and diffusion- controlled oxidation process with potential and peak current values pH dependent. This biocide can be determined by square-wave voltammetry (SWV) with a linear response up to 53 mg L−1. Using an adsorptive stripping approach prior to the square-wave voltammetry (SWAdSV) it is possible to analyse samples containing very low concentrations of MIT, with a limit of detection of 0.0080 mg L−1. Both SWV and SWAdSV methods were applied with successful results to determine MIT in different water samples.