This article employs Labour Force Survey data, using logistic regression modelling, to help rectify the lack of systematic analyses specifically into socioeconomic correlates of migrant workers’ unionisation in Britain. The results provide evidence to assist the development of comprehensive explanations for the obstacles behind migrant workers’ unionisation. The impediments analysed can be considered within what one might call a triple-challenge model comprising of (1) encounter inputs: demographic factors brought into the host society and citizenry rights offered by the host society to migrant workers; (2) accentuated structural factors: workplace characteristics, flexible work and migrant workers’ disproportionate location in less unionised companies with flexible contracts; and (3) knock-on effects: educational and occupational influences along with the impacts of encounter inputs and accentuated structural factors on such influences.