BACKGROUND: The workload service users and caregivers take on, and their capacity to do this work, when they engage with and participate in different kinds of care is important. It is reflected in policy and practice interventions that identify service users and caregivers as part of a team that consists of informal networks beyond provider organisations and the professionals within them in health and social care. AIMS AND OBJECTIVES: To synthesise qualitative studies of the lived experience of the work of service user and caregiver engagement in three kinds of conditions: long-term conditions associated with significant disability (Parkinson's disease, schizophrenia); serious relapsing-remitting disease (inflammatory bowel disease, bipolar disorder); and rapidly progressing acute disease (brain cancer, early-onset dementia). DESIGN: Theory-informed qualitative evidence synthesis of primary qualitative studies, qualitative systematic reviews and meta-syntheses. Papers analysed using qualitative attribution analysis, and Event-State Modelling. DATA SOURCES: Cumulative Index to Nursing and Allied Health Literature, EMBASE, MEDLINE, PsycInfo, Scopus and Social Care Online were searched from January 2010 to April 2021. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Qualitative primary studies, systematic reviews and meta-syntheses where the participants were service users, or caregivers, aged ≥ 18, with one of six index conditions, and which described their lived experiences of care. METHODS: Qualitative evidence synthesis to model core components of service user and caregiver work, and to identify common factors across index conditions, disease trajectories and service contexts. RESULTS: Searches identified 34,787 records. Following deduplication, 13,234 records were assessed for relevance, and after first-stage screening, 7782 records were excluded at this stage, leaving 5452 for further screening, and 279 of these met inclusion criteria and were included in the evidence synthesis. These showed that patients' and caregivers' lived experiences of illness trajectories were shaped by mechanisms of enabling agency (personal capacity, social capital, affective contributions of others), and their degree of existential threat, competence in managing processes of care, and caregiver responses to new responsibilities. Their degree of structural disadvantage was framed in terms of loss of income, employment and housing, and by the presence of stigma, rather than by intersectional position and socioeconomic status. CONCLUSIONS: This evidence synthesis maps intervention points to support service users and caregivers, and the trajectories of work that frame their effective participation in their care. We identify potential targets for interventions that could support their outward-facing work as they seek to mobilise agency, sustain personal capacity, maintain their social capital and draw on the affective contributions of others. LIMITATIONS: Our pragmatic search strategies led to a maximum variation sample of studies of lived experiences of index conditions but may have missed relevant studies. No papers with an explicit social care focus were discovered for brain cancer, bipolar disorder and inflammatory bowel disease. Most studies were descriptive, and samples and methods were often poorly described. FUTURE WORK: Future research should explore interactions between personal capacity, social capital and affective contributions, in lived experiences of service users and caregivers. STUDY REGISTRATION: This study is registered as PROSPERO CRD42020224787. FUNDING: This award was funded by the National Institute for Health and Care Research (NIHR) Health and Social Care Delivery Research programme (NIHR award ref: NIHR130407) and is published in full in ; Vol. 13, No. 24. See the NIHR Funding and Awards website for further award information.