In recent years, impacts of multiple social identities has been focused. The purpose of this study was to assess the relationship between awareness of multiple social identities and discrimination, and life satisfaction, considering the mediating effect of attitude toward outgroup members. An online survey was conducted with 386 participants (male = 178, female = 208). Latent profile analysis based on three group identification variables (sex, age, Japanese) suggested two clusters: high and low awareness of multiple social identities. When awareness of multiple social identities was high, life satisfaction and awareness of discrimination were also high, and attitude toward outgroup members was favorable. Additionally, the results of multiple group structural equation modeling indicated that attitude toward outgroup members mediated the relationship between awareness of discrimination and life satisfaction, when awareness of multiple social identities was high. The impact of awareness of multiple social identities on psychological well-being is discussed.