The extension of attachment principles to adults’ close relationships provides an important theoretical framework for understanding how romantic partners behave in the face of conflictrelated events. The present study employed a cross-sectional, questionnaire design, to investigate attachment-related differences in the relationship behaviours of participants recruited from the researchers’ social networks (N = 343). Using a mediational model, the study examined the influence of insecure attachment (avoidance and anxiety) on the maladaptive attributions couples make for partner behaviour in a conflict-related event, and how this impacts on perceptions of relationship quality. Additionally, the study investigated the importance of attachment avoidance and attachment anxiety in predicting relationship quality, when compared to previously established personality measures of neuroticism and extraversion. This study is the first of its kind to integrate all of these variables. Results supported the hypothesised association of attachment anxiety with poor relationship quality, as mediated by attributions. In contrast, the association between attachment avoidance and poor relationship quality was not mediated by attributions. Attachment anxiety and avoidance were found to be better predictors of relationship quality than neuroticism and extraversion. Overall, the results provide support for attachment theory, highlighting the negative implications of attachment insecurities for responses to couple conflict and for relationship functioning. The findings may be applied to clinical settings, in order to reduce the negative impact of attachment insecurities on couple conflict behaviours and on the quality of romantic relationships.