Biological activity in the surface ocean leads to emissions of methanethiol (MeSH) and dimethyl sulfide (DMS). Measurements of MeSH in the marine atmosphere are sparse and the impact of NOx pollution on MeSH oxidation remains unexplored. We present measurements of MeSH and DMS at a coastal site with NOx concentrations up to 24.3 ppb in the United Kingdom during May and June. Winds coming from the seaward (northerly) direction showed a median (25th quantiles) MeSH mole fraction of 15.7 (7.9-26.9) ppt. Mole fractions were generally higher in winds coming from the sea over those from land. The measurements reveal significantly lower MeSH during daytime. Using an atmospheric box model, we suggest substantial night-time oxidation of MeSH by NO3 and that NOx pollution has the potential to reduce the SO2 yield from MeSH. This work confirms the prevalence of MeSH and illustrates the impact of NOx pollution on MeSH oxidation.