Using a global model, we investigate how bromine chemistry affects cloud condensation nuclei (CCN) formation in the remote marine atmosphere. Bromine increases dimethylsulphide (DMS) oxidation but lowers SO2 yield, leading to less sulphate aerosol. The effect is largest (3–7% decrease in total CCN and 15–30% decrease in CCN from DMS) over the summertime southern ocean, a region of strong bromine release from sea-salt. DMS and bromine emissions have a coupled feedback effect on CCN. Increased DMS enhances the release of sea-salt bromine through increased aerosol acidity. This enhanced bromine suppresses the CCN response to increased DMS by up to 30%.