Background: Specialist palliative care (SPC) providers tend to use the term ‘complex need’ to refer to the needs of patients who require SPC. However, little is known about “complex needs” on first referral to a SPC service. We examined which needs are present and sought the perspectives of healthcare professionals on the complexity of need on first referral to a hospice service. Methods: Multi-site sequential explanatory mixed method study consisting of a case-note review and focus groups with healthcare professionals in four UK hospices. Results: Documentation relating to 239 new patient referrals to hospice was reviewed; and focus groups involving 22 healthcare professionals conducted. Most patients had two or more needs documented on referral (96%); and needs were recorded across two or more domains for 62%. Physical needs were recorded for 91% of patients; psychological needs were recorded for 59%. Spiritual needs were rarely documented. Referral forms were considered limited for capturing complex needs. Referrals were perceived as influenced by the experience and confidence of the referrer and the local resource available to meet palliative care needs directly.Conclusions: Complexity was hard to detail or to objectively define on referral documentation alone. It appeared to be a term used to describe patients whom primary or secondary care providers felt needed specialist palliative care knowledge or support to meet their needs. Education and training in palliative care for primary care nurses and doctors and hospital clinicians could reduce the need for referral and help ensure that hospices are available to those most in need of specialist palliative care input.