Intimate intergroup contact is considered an optimal form of contact for reducing prejudice, yet less is known about how such relationships develop among ethnic minority adolescents in the Chinese cultural context. Using convenience sampling, data were collected from 668 Tibetan adolescents in Gansu, China. Guided by self-expansion theory and intergroup contact theory, this study examined the association between self-expansion motivation and cross-ethnic intimate contact, together with its mediating and moderating mechanisms. Self-expansion motivation, cross-ethnic friendship self-efficacy, and contact behavioral intention were positively correlated with cross-ethnic intimate contact. Cross-ethnic friendship self-efficacy and contact behavioral intention formed a significant chain mediating pathway. Gender moderated the association between self-expansion motivation and cross-ethnic friendship self-efficacy, and the indirect effects involving cross-ethnic friendship self-efficacy were stronger for boys than for girls. Self-expansion motivation may foster cross-ethnic intimate contact through cross-ethnic friendship self-efficacy and contact behavioral intention. Schools may promote such contact by integrating self-expansion-oriented activities into interethnic interaction and by providing targeted support to strengthen girls’ cross-ethnic friendship self-efficacy.