A growing literature suggests that there is cross-cultural variation in levels of autism-related stigma, which may partially be explained by differences in cultural orientation or autism-related knowledge between countries. This literature has relied heavily on self-report measures of explicit attitudes towards autism; little research has examined implicit biases, and whether these implicit biases vary across cultures. Thus, here we had two aims: (1) to assess the contribution of knowledge and cultural orientation to "both" explicit stigma and implicit biases, and (2) to compare autism-related knowledge, explicit stigma, and implicit biases across university students in Hong Kong (n = 119), the United Kingdom (n = 120), and the United States (n = 122). Replicating prior work, we found that explicit stigma was predicted by less accurate knowledge, lower horizontal collectivism, greater vertical individualism, and higher implicit biases. Implicit biases were "directly" predicted by age and explicit stigma, and "indirectly" predicted by vertical individualism (positively) and horizontal collectivism (negatively) via explicit stigma. Knowledge and explicit stigma differed across countries, even after accounting for covariates: students in Hong Kong displayed less accurate knowledge, and higher explicit stigma towards autism, than those in the United Kingdom and United States. However, implicit biases did not differ between countries.