The purpose of this research is to examine the association between attachment insecurities (anxiety and avoidance) and both subjective well‐being (positive and negative affect and life satisfaction) and relationship satisfaction. 174 Spanish heterosexual couples with a mean length of relationship of 13.9 years participated in the study. The hypotheses were tested according to the Actor‐Partner Interdependence Model (APIM). We proposed a model in which positive affect (PA) and negative affect (NA) could mediate the association between attachment insecurities and life and relationship satisfaction. Results show that: 1) actor effects are more frequent than partner effects; 2) anxious attachment tends to be related to NA and avoidant attachment to PA; 3) avoidance is more detrimental than anxiety for relationship satisfaction at individual and dyadic levels, and 4) there are some mediational effects of NA and PA in the association between attachment insecurities and life and relationship satisfaction.