Abstract The societal shift toward greater gender equality has led to increased variability in people’s gender role attitudes, or the belief that men and women should occupy distinct family roles (i.e. men as breadwinners and women as homemakers). Existing evidence on the association between gender role attitudes and relationship well-being remains inconclusive with mixed findings, likely because past research has not adequately considered the direction and degree of (in)congruencies between partners within the relationship. Using longitudinal samples of 1,327 couples from the United States and 5,856 couples from Germany tracked over 2 and 13 years, respectively, we employed dyadic response surface analysis to examine how different patterns of partner (in)congruencies in gender role attitudes predict relationship well-being in mixed-gender relationships. The results showed that, for US men and German men and women, the direction of incongruence between partners’ gender role attitudes mattered: relationship satisfaction was higher when men adopted more egalitarian attitudes than women (or conversely, when women adopted more traditional attitudes than men) compared with the reverse. Relationship satisfaction was also higher when both partners showed congruence in extreme gender role attitudes (either strongly traditional or egalitarian) than when either partner endorsed more neutral attitudes. US women reported higher relationship satisfaction only when either partner endorsed more egalitarian attitudes. Although past research emphasizes the benefits of partner similarity for relationship well-being, our findings highlight the importance of both similarity and complementarity in gender role attitudes, potentially subject to cultural and contextual factors. <<<