Dissociative identity disorder and depersonalization-derealization have attracted research and clinical interest, facilitating greater understanding. However, little is known about the experience of multiplicity of self outside of traumagenic or illness constructs. Consequently, this systematic review explored how people identifying as having multiple selves conceptualize their experiences and identity. A comprehensive search of qualitative studies reporting lived experiences of multiplicity was conducted through PsycINFO, PubMed and Scopus (PROSPERO ID: CRD42021258555). Thirteen relevant studies were retrieved (N = 98, 16-64 years, conducted in the United Kingdom, the United States, Hungary and Poland). Using line-by-line thematic synthesis, four analytical themes were developed: multiplicity: disorder versus experience; impact of understanding multiplicity; importance of supporting multiplicity; and continuum of experiences. This review highlights heterogeneity within multiplicity-spectrum experiences, emphasizing the need for person-centred, individualized understanding, separate from mental health conceptualizations. Therefore, training in person-centred individualized care to promote self-concept clarity is needed across health, education and social care. This systematic review is the first to synthesize voices of people with lived experience across the multiplicity spectrum, demonstrating how qualitative research can contribute to advancing our understanding of this complex phenomena with the community, acknowledging reciprocal psychosocial impacts of multiplicity and providing valuable recommendations for services. [Abstract copyright: © 2023 The Authors. Clinical Psychology & Psychotherapy published by John Wiley & Sons Ltd.]