Although acculturation is considered a mutual process, no measure assesses attitudes toward mutual acculturation. Through a novel four-dimensional measurement, this study addresses this research gap by assessing attitudes toward minority and majority acculturation and its relation to psychological adjustment for immigrant-background minority and non-immigrant majority adolescents in public secondary schools in three European countries: in Germany (n = 346, 46% female, Mage = 12.78 years, range 11–16), Greece (n = 439, 56% female, Mage = 12.29 years, range 11–20), and Switzerland (n = 375, 47% female, Mage = 12.67 years, range 11–15). Latent profile analyses led to three distinct acculturation profiles in all three countries: strong and mild mutual integration profiles, where both migrant and majority students are expected to integrate, and a third profile assuming lower responsibility upon the majority. Additionally, those in the strong- and mild-integration profiles reported stronger psychological adjustment than those assuming lower responsibility upon the majority, which held for all students in Switzerland and mostly for those without a migration background in Germany. The findings demonstrate the importance of a mutual acculturation framework for future research. Moreover, as most adolescents fit in with one of the mutual integration patterns, findings stress that no matter their migration background, adolescents favor mutual integration including the expectation on schools to enhance intercultural contact.