The couple relationship is an essential source of support for individuals undergoing psychological treatment and the aim of this study was to apply a new methodology in assessing the quality of such support. A theoretically informed thematic analysis of interview transcripts was conducted, triangulated by quantitative data. Twenty-one brief psychotherapy outpatients were interviewed on their couple relationships before they embarked on cognitive analytic therapy. Patients suffered from a variety of psychological difficulties, including anxiety, depression and personality disorder. Thematic analysis captured empirically eight components of couple attachment as proposed by theory. Thematic analysis also suggested that these components defined four overarching relationship themes, indicating different types of relational difficulties experienced by the patients. Triangulation with quantitative data suggested that relationship themes were unrelated to severity and type of patient pathology but were associated with the duration of the relationship. A stage theory of couple attachment formation may provide a useful framework for understanding the findings.