Carers of people with mental illness frequently report interpersonal difficulties in their caring relationship, and experiential avoidance likely contributes to these problems. This study aimed to examine the relationship between experiential avoidance and eight interpersonal problem domains amongst lay mental health carers, and tested the mediating role of attachment anxiety and hostility. In addition, an alternative (reverse) mediation was tested in which experiential avoidance played the mediating role. A cross-sectional community-based sample of 145 mental health carers completed a questionnaire containing demographics and measures of interpersonal problems, experiential avoidance, attachment anxiety and hostility. Results indicated the relationship between experiential avoidance and interpersonal problems was fully mediated for the interpersonal problem domains of cold/distant and socially inhibited. Partial mediation was evident for the vindictive/self-centered, non-assertive, overly accommodating, self-sacrificing and intrusive/needy domains. No mediation occurred for the domineering/controlling domain. Alternative (reverse) model findings indicated partial/full mediation for the overly accommodating, domineering/controlling and vindictive/self-centered domains, and no mediation for the remaining five domains. Although tentative, findings suggest a mechanism for the relationship between experiential avoidance and particular domains of interpersonal problems that warrants further investigation. The importance of our data is highlighted by the burden and difficult relationships experienced by mental health carers, that requires targeted and effective psychological treatment.