The aim of this review was to propose and describe the design and delivery of an attachment-informed general mental health service. We systematically searched the PsycINFO, MEDLINE, Web of Knowledge, COPAC, CINAHL, and Science Direct databases from 1960 to 2013. We also searched reference lists of relevant papers and directly contacted authors in the field. Literature describing attachment theory and its applicability in designing and delivering general mental health services was synthesized using thematic analysis. Papers published in English, books or chapters in edited books that described applying attachment theory in designing and delivering mental health services for adults and adolescents were included in the review. Of the 1,105 articles identified, 14 met inclusion criteria for the review. Eight key themes, and four subthemes, were extracted and organized to reflect the experience of a service user moving through the mental health system. Key themes extracted were as follows: service policy and evaluation; referrals; assessment and formulation; intervention; support for staff; support for carers; moving on; and potential service benefits. Papers reviewed suggested that service users with severe mental health problems have attachment needs that should be met in general mental health services. Attachment theory provides a useful framework to inform the design and delivery of general mental health services. The resource implications for services are discussed, as are limitations of the review and recommendations for future research. Attachment theory should be used to inform the design and delivery of general mental health services. Mental health services should evaluate the extent to which they meet service users' attachment needs. Attachment-informed mental health services should assess outcomes, including cost-effectiveness over time. Papers included in this review focus on long-stay residential care or secure services and there is a limited experimental evidence base to show that providing an attachment-informed service improves patient outcomes.