We investigated the nature of prejudice toward people with developmental disabilities, its potential roots in dehumanization, its implications for social policy beliefs affecting this target group, and strategies for reducing prejudice toward people with developmental disabilities. Studies 1 (N = 196, MTurk) and 2 (N = 296, undergraduates) tested whether prejudice took a hostile or ambivalent (both hostile and benevolent components) form. Consistent support for a hostile prejudice model was found. This model was comprised of beliefs that people with developmental disabilities may harm others, should be kept separate from others, and are dependent on others. Also, greater dehumanization was associated with greater prejudice, and prejudice mediated the effect of dehumanization on participants' social policy beliefs. Study 3 (N = 151, MTurk) provided construct validity for the newly developed multidimensional measure of prejudice. Study 4 (N = 156, undergraduates) showed that presenting a person with developmental disabilities in either humanizing or individuating ways reduced dehumanization and prejudice and, in turn, increased the favorability of social policy beliefs.