Purpose: Stigma reduction is an important public health challenge because of the large morbidity and mortality associated with some forms of substance use. Extreme stigma can lead to dehumanisation of target groups, who are ascribed with lesser humanity. The authors examined whether there was blatant and subtle dehumanisation of people who use heroin, and if these were associated with levels of support for non-discriminatory drug policy. Design/methodology/approach: A cross-sectional online study using a UK convenience sample (n = 307 [75.2% female, mean age 28.6 ± 12.2 years]) was conducted. Participants completed assessments of blatant (Ascent of Humans [AoH] scale) and subtle (an emotion attribution task) dehumanisation and a bespoke measure assessing support for non-discriminatory drug policies. Other measures controlled for stigma towards people who use drugs (PWUD) and moral disgust. Findings: There was greater blatant dehumanisation of people who used heroin compared to the general population and other potentially stigmatised reference groups, including people who use cannabis. The authors also found evidence of subtle dehumanisation, and people who used heroin were rated as being less likely to feel uniquely human emotions, less likely to feel positive emotions and more likely to feel negative emotions. Blatant dehumanisation was associated with significantly lower probability of support for non-discriminatory drug policy. Social implications: Dehumanisation may present significant challenges for stigma reduction initiatives and in fostering public support for drug policy and treatment. Denial of the humanity of this group could be used to justify discriminatory policies or relative deprioritisation of support services in funding decisions. Activities that seek to "rehumanise" PWUD, including social inclusion, and encouraging compassionate media representations that portray the lived experiences of substance use may be useful areas of future work. Originality/value: This is the first study to investigate blatant and subtle dehumanisation of people who use heroin, and how this relates to public support for drug policy.