I outline different beliefs about assimilation, and show that these beliefs can influence attitudes toward immigration. Using data from a new national sample survey in Japan, I test whether and how beliefs about assimilation influence attitudes toward immigration. The results show two important conclusions. First, there is a large anti-immigrant sentiment in Japan. Second, after controlling for other known determinants of attitudes toward immigration, I find that those who are in favor of immigrant assimilation support higher levels of immigration, more immigrant equal rights, and have more accurate views about immigrant crime in Japan. This suggests that those favoring assimilation are not necessarily xenophobic in all cultures.