Researchers exploring the role of psychological essentialism in the folk-sociological domain have typically focused on social categories that are commonly perceived to be determined by some form of underlying biological basis. Meanwhile, the relatively scarce studies of essentialist representations of socio-economic categories have predominantly been conducted in cultural contexts in which socio-economic differences and the concept of ‘class’ are either conflated with the overtly naturalising logic of caste or, conversely, submerged beneath an ostensibly meritocratic and egalitarian ethos. Yet even here attention is given primarily to natural kind-like and folk-biological intuitions. However, several developments in psychological research have suggested that naturalisation is neither a necessary nor sufficient feature of essentialism, particularly where group identity and category-typical characteristics are understood to be transmitted through the process of socialisation, for example in social determinist beliefs concerning socio-economic background. This chapter examines how the components of psychological essentialism are manifested within socially mobile individuals’ conceptualisations of socio-economic categories and the experience of social mobility in the UK. Interviewees’ responses clearly demonstrate that an individual’s socio-economic background is sometimes believed to be identity-determining and that this identity is both inherent and ultimately immutable.