Background: People with profound intellectual disabilities are a population with complex comorbidities. Total pain recognises the interconnectedness of aspects of pain; social, psychological, physical, emotional, spiritual. Pain is under-recognised due to communication challenges and carers perceptions. This review's purpose is to synthesise current literature and provide guidance for future research and care.Methods: Five databases were searched in this mixed methods systematic review (Cinahl, Medline, Psycinfo, Web of Science, Scopus). Articles retrieved were reported via a PRISMA flow diagram. Quality appraisal utilised the mixed methods appraisal tool (MMAT). A convergent qualitative design was the method of data synthesis. Results: Data from 16 included articles generated four themes; Absent voices, reductionist assessment, pain intensity, valuing expertise. Data included physical pain only. Conclusion: Multifaceted pain needs inclusion in research. Assessment must consider the unique expressions of pain by individuals with profound intellectual disabilities. A sharing of expertise may improve pain care. K E Y W O R D S assessment, pain, pain scales, perceptions, profound intellectual disabilities, suffering 1 | BACKGROUND Pain is a subjective unpleasant experience which has a negative effect on an individual's functional ability, and emotional state (Mehta & Chan, 2008). Davis (2000, p. 1) defined pain as involving 'all aspects of our nature from our physiology and biochemistry to our emotional and motivational make up, to our psychological processes and being, to our social relationships and to our sense of spiritual awareness'. It is understood as a multifaceted experience by pivotal authors, incorporating physical, psychological, social and spiritual domains (Cassell, 2004;Saunders, 1993). The interconnectedness of these components interacting upon one another is believed to result in a total pain experience which is specific to each person's particular situation (Krok et al., 2022;Mehta & Chan, 2008;Saunders, 1993).People with profound intellectual disabilities are a population with a very high prevalence of multi-morbidities and chronic pain, and communication challenges can impede the recognition and assessment of this pain (Doody & Bailey, 2017a;McGuire et al., 2010).Understanding that for people with profound intellectual disabilities, pain caused by physical, psychological, social and spiritual factors may contribute to the person's pain experience is essential as a basis for pain assessment. For example an individual may experience chronic physical pain and their distress may increase due to different factors, dependent on the individual, such as changes in surroundings, unfamiliar faces, grief. A person's usual pain behaviours, behaviours of