The cognitive tools humans use to perceive and name reality are social constructs that necessitate critical examination. ‘Gender’ and ‘sex’ are socially constructed categories used in daily life and in relation to occupations, that warrant scrutiny, as traditional explanations for gender differences based on biology fail to account for the social processes that construct gendered groups. Questioning the naturalness of these categories is essential for understanding how they shape individual capabilities and social norms around occupations. This discussion paper adopts a materialist feminist standpoint to problematize the concepts of gender and sex. Rejecting biological essentialism, we argue that social organization precedes and constructs the significance of sex categories. By reconceptualizing both gender and sex as socially constructed, our analysis challenges notions of gender as culture applied to a pre-existing biological sex. Occupational literature makes use of these categories to explore gender-related issues. It mainly focuses on gender identity through an interactional orientation that, nevertheless, preserves an individual conception. Social categories are also used to illustrate inequalities and contextual factors related to gender; an essential usage that remains at risk of reifying such categories as pre-existing groups. The use of gender as a social system of hierarchical bi-categorization, as we propose, is not present in occupational literature. This materialist feminist analysis underscores the importance of questioning entrenched biological determinism of sex, on which rests gender as identity. In highlighting the social construction of categories, occupational science can contribute to a deeper understanding of occupation within, and in the challenge of, oppressive systems.