Cancer cachexia has a negative impact on patients and their informal caregivers but as there are no approved drug treatments for the condition, palliation of symptoms is the main therapeutic goal. This thesis describes the development and piloting of a workshop, the first small group psychoeducational intervention for cancer cachexia. The main objective of the workshop was to improve the quality of life (QOL) of patients and carers. A new questionnaire, the QLQ-CAX24 was developed to assess QOL in patients with cancer cachexia. A study to explore the feasibility of conducting a randomised controlled trial (RCT) using the workshop in a secondary care setting was conducted. Workshop development was consistent with the MRC guidelines for developing and evaluating complex interventions and development followed the Coventry Intervention Development Process. A systematic review of the patient literature generated a comprehensive list of QOL issues and was used to develop a model of the patient experience of cancer cachexia. This model, along with the Integrated Theory of Health Behaviour Change provides the theoretical underpinning of the workshop. The patient systematic review supplemented interviews with patient and health care professional (HCP) interviews in the development of the QLQ-CAX24. A systematic review of the carer literature was limited by the available data but domains of experience were identified. The intervention targets of the workshop were identified by carrying out interviews with patients, carers and HCPs and by consulting the patient and carer systematic reviews. The published literature and other cancer cachexia interventions informed the content of the workshop, both in terms of the information it provides and the methods used to deliver this information. Pilot and feasibility testing demonstrated that although the workshop was acceptable, a different recruitment strategy is required for the planned RCT.