The study of multicultural identity has gained prominence in recent decades and will be even more urgent as the mobility of individuals and social groups becomes the "new normal." This paper reviews the state-of-the-art theoretical advancements and empirical discoveries of multicultural identity processes at the intrapersonal, interpersonal, and collective (e.g., organizational, societal) levels. First, biculturalism has more benefits for individuals’ psychological and sociocultural adjustment than monoculturalism. Bicultural individuals’ racial essentialist beliefs and Bicultural Identity Integration affect cultural frame switching, racial categorization, and creativity. Second, identity denial and identity-based discrimination by other people or groups threaten multicultural individuals’ psychological health and performance. Third, multiculturalism and interculturalism policies are associated with different conceptions of and attitudes toward diversity, and have distinct outcomes for multicultural individuals and societies.