This paper examines the psychological well-being of high school adolescents immigrating from Russia and Ukraine to Israel without parents. Data were collected in a 3-year longitudinal study that covered the premigration through postmigration periods. Immigrant adolescents were compared with nonemigrating adolescents in Russia and Ukraine. Psychological well-being of immigrants was highest in the premigration period. During the process of immigration, general self-esteem, body image, social competence, school competence, and loneliness followed a U-curve: they declined in the 1st year after immigration and improved in the 3rd year after immigration. Emotional and behavioral problems of immigrants increased in the 1st year after immigration and did not change in subsequent years. At the end of the 3-year period, self-esteem exceeded the premigration level, emotional and behavioral problems and loneliness remained below the premigration level, while body image, social competence, and school competence returned to the premigration level. Throughout the entire immigration period, the psychological well-being of immigrants was higher than that of nonemigrating adolescents. Premigration psychological well-being as well as perceived social conditions in the host country (discrimination and social support) predicted postmigration psychological well-being. The results obtained are discussed in light of the stress-coping model of immigration and ecological systems theory.