Individuals’ reaction tendencies in emotional situations may influence their social relationships. In two studies, we examined whether perceived similarity in emotional reaction tendencies between the self and a close other was associated with individuals’ emotional well-being. Participants rated how the self and a close other (mother in Study 1; a self-nominated close other in Study 2) would react in various situations. Individuals who perceived greater similarity between the self and the close other reported more positive affect, less negative affect, lower perceived stress, and higher life satisfaction than those who perceived less self–other similarity. Furthermore, stress exposure moderated the effects of self–other similarity on perceived stress. In summary, greater perceived similarity with one’s close others seems beneficial for social–emotional adaptation.