Understanding dyadic personality configurations and their associations with marital quality helps identify couples who are at high risk of marital strain. However, current research on personality similarity among spouses usually confounds couples with similarly positive and similarly negative personalities. This study aimed to (1) provide a clearer classification of dyadic personality profiles among older couples, (2) examine the associations between these profiles and both partners’ marital quality, and (3) explore gender differences in these associations. Data came from 3,178 older couples drawn from the 2010/2012 waves of the Health and Retirement Study. Latent profile analysis was used to identify dyadic personality profiles based on spouses’ standardized Big Five personality scores. Multilevel models examined associations between dyadic personality profiles and each partner’s marital quality, testing for gender differences as well. Six dyadic personality profiles were identified, including two opposite profiles (52%; positive wife–negative husband and positive husband–negative wife), two similar profiles (40%; similarly positive and similarly negative), and two extreme profiles (8%; extremely negative husband and extremely negative wife). Couples in the similarly positive profile reported the best marital quality, whereas couples in the similarly negative profile and the two extreme profiles reported the worst marital quality. The associations between profiles characterized by negative traits and marital quality were more pronounced among wives than husbands. This study advances the understanding of personality similarity and its consequences, suggesting heterogeneous subgroups of dyadic personalities among older couples and providing evidence of gender differences in the implications of personality similarity for relationship quality.