Ethnic Russians in Estonia, who previously enjoyed a privileged status in the Soviet era, have become a relatively deprived group with devalued group identity in the new Estonian state. We examined acculturation (cultural maintenance and participation) and perceived group devaluation of ethnic Russians (N = 190) as predictors of their well-being and ethnic attitudes toward native Estonians. The results of surveys revealed that participation in Estonian culture predicted more positive ethnic attitudes; however, Russian cultural maintenance and perceived group devaluation were associated with both negative ethnic attitudes and lower life satisfaction. Significant interactions also emerged. Perceived group devaluation dampened the positive relation between participation and ethnic attitudes and exacerbated the negative relation between cultural maintenance and ethnic attitudes. Participation was associated with higher well-being under conditions of low perceived group devaluation but poorer well-being when group devaluation was perceived as high. Similarly, an interaction between the acculturation dimensions of maintenance and participation demonstrated that participation in Estonian culture was associated with lower life satisfaction under the conditions of high cultural maintenance. The key findings on cultural maintenance and the “failure” of integration are distinctive in the light of previous studies and point to the important implications of contextual sociopolitical and historical factors for well-being and ethnic relations in a culturally diverse society.