Women are more likely than men to be sexualized, objectified, and dehumanized. Female sex workers experience stigma and violence associated with these judgements at far higher rates than other women. Here, we use a pre-registered experimental design to consider which aspects of sex work – the level of sexual activity, earned income, or perceived autonomy of the work – drive dehumanization. A first group of participants (N = 217) rated 80 vignettes of women varying by full-time employment, hobbies and interests on humanness. These ratings were subtracted from the ratings of a second group of participants (N = 774) who rated these same vignettes which additionally described a part-time job, hobby or activity that varied in sexual activity, income earned and autonomy over one’s actions. We find that women and especially men dehumanize women they believe are engaging in penetrative sex. We also find that women’s autonomy of, but not their income from, their sexual activity increases dehumanization. Our findings suggest that opposition to women’s ability to pursue casual sex and generalizations about the exploitative conditions of sex work may drive the harshest negative prejudice towards female sex workers and, by similar mechanisms, women’s sexuality in general.