The present study investigated the relationship between Hong Kong people's stereotype toward Mainland people and their own national attachment (i.e., national identity, constructive patriotism, and uncritical patriotism). The role of inter-group relationship as mediator and age as moderator of that relationship were also tested. A total of 1753 local Hong Kong people aged 17-80 (mean age = 20.35 years, SD = 5.02) completed anonymous questionnaires regarding their stereotypes toward Mainland people, inter-group relationship with Mainland people, and national attachment. As expected, stereotypes toward Mainland people, inter-group relationship and national attachment showed significant positive associations with each other. More interestingly, it was found that the inter-group relationship mediated the relationship between stereotypes toward Mainland people and three domains of national attachment, with this indirect link being weaker for younger Hong Kong adults than for older Hong Kong adults. Implications of the present findings for future research are discussed, as well as potential interventions for increasing subjective national attachment to China, especially in young Hong Kong people. [ABSTRACT FROM AUTHOR]