Background It has been suggested that mental health services can help meet the attachment needs of inpatients and improve patient outcomes through the provision of a ‘secure base’; however, what defines the latter is unclear. Perception of ward climate might be a useful indicator. Aim The aim of this study was to examine whether inpatient perceptions of the ward climate, which is partly under the control of the service, or inpatients' own personal levels of attachment anxiety and avoidance are more associated with their attachment to their service. Method Seventy‐six men diagnosed with a psychotic illness, who were residents in one of four regional medium‐security units in England, completed questionnaire measures of service attachment, personal attachment style and ward climate. Results Ward climate was more strongly associated with service attachment than personal levels of attachment anxiety and avoidance. The most important aspect of ward climate for service attachment was the depth and influence of staff support for the inpatients. Conclusions Although patient characteristics are important influences on development of service attachment, ward climate is also important. The latter may be easily and reliably monitored with a brief questionnaire. Strategies to enhance and maintain its positive components are likely to be important for progress with forensic hospital inpatients who have a psychotic illness. Copyright © 2013 John Wiley & Sons, Ltd.